How can a person know whether finding things being made easy for him and having his prayers answered does not come under the heading of being led step-by-step to his ruin?

Firstly: 

The believer always thinks positively of his Lord and
negatively of his own self; nothing bad happens to him but he knows that
what befell him only befell him as a result of his sin, and nothing good
that he loves ever comes to him but he knows that it is by the grace and
blessing of his Lord towards him, out of His kindness and generosity.

Secondly: 

Supplication is of two types: 

·       
supplication as an act of
worship; the Muslim should constantly be in a state of worship and obedience
towards his Lord;

·       
and the supplication of
asking, which is asking Allah to bring benefit and ward off harm. 

The supplication of worship is only for believers. As for the
supplication of asking, it is for both believers and disbelievers, righteous
and evildoers. Not everyone whose prayers are answered is one with whom
Allah is pleased and loves, or is pleased with his deeds. This is in
contrast to the supplication of worship, which can only be done with the
help of Allah, may He be exalted, and is an indication of His love for that
person. 

Hence the answer to a prayer may be by way of leading a
person, step-by-step, to his ruin, or it may be hastening his share of
goodness, so that it is limited to him in this life only; or it may be by
way of Allah showing His mercy to His slaves, or it may be an answer to the
prayer of one who has been wronged, and so on. Or it may be because of a
person’s righteousness and piety. 

To sum up: supplication is one of the means of meeting one’s
needs; in fact it is one of the greatest means. If the need is a worldly
matter and the supplication is answered, then that is provision from Allah
that he has attained by means of the supplication, just as work is also a
means of attaining provision, getting married is a means of having children,
and treating sickness is a means of healing. But being granted provision,
and the hastening thereof, is not an indication that Allah loves the one to
whom He granted that provision, just as a lack of response or withholding of
provision is not an indication that Allah is angry with the one from whom he
withheld it. 

For more information and further clarification, please see
the answers to questions no. 41114 and
177561 

Thirdly: 

Giving and withholding, lowering and raising, wealth and
poverty, health and sickness, and all that Allah decrees for His slave of
provision, is all in the hands of Allah alone; He decrees it and sends it to
whomever He wills of his slaves. None of His creation – neither the Shaytaan
and his helpers, nor the angels, nor any created being – has the power to do
any of that independently, and no one shares with Allah, may He be exalted,
in the control of any of these matters. All of that is entirely in the hand
of Allah. Having established that, this does not mean that people cannot be
the means of any of the things mentioned above. As healing is only in the
hand of Allah, the doctor is but the means; having a child is something
granted by Allah, and the husband or wife is a means, and so on. 

It was narrated and classed as saheeh by at-Tirmidhi (2516),
from Ibn ‘Abbaas (may Allah be pleased with him) that the Prophet (blessings
and peace of Allah be upon him) said: “… Know that if the entire nation were
to come together to benefit you with something, they would never benefit you
except with something that Allah had decreed for you; and if they were to
come together to harm you with something, they would never harm you except
with something that Allah had decreed against you. The pens have been lifted
and the pages have dried.”

Classed as saheeh by al-Albaani in
Saheeh at-Tirmidhi 

Fourthly: 

Leading someone step-by-step to ruin and allowing him to get
carried away in sin is not an action of the Shaytaan at all, and he has
nothing to do with it whatsoever. Nothing of that nature is attributed to
him in the Book of Allah, or in the Sunnah of His Messenger (blessings and
peace of Allah be upon him). He does not have the power to meet a person’s
needs for the purpose of leading him step-by-step to ruin, nor does he have
the power to withhold anything from him in order to lead him step-by-step to
ruin. Allah, may He be exalted, has limited his stratagems to whispering and
tempting people. As for control and disposing of people’s affairs, he has no
such power at all. 

Rather leading people step-by-step to their ruin is something
that Allah, may He be exalted, does to whomever He wills of His slaves. 

Imam at-Tabari (may Allah have mercy on him) said: 

The basic meaning of leading someone step-by-step to his ruin
is when the one who is subject to that misinterprets the kindness of the one
who does that to him, so that the one who is subject to that thinks that the
one who is doing it to him is being very kind to him, until he finds himself
in trouble.

End quote from Tafseer as-Sa‘di (13/287) 

The individual should think more positively of Allah with
regard to what He has bestowed upon him of blessings, but he should also pay
attention to giving thanks for it, and combine that with fearing the plan of
Allah. Thus in his journey to Allah he should combine fear and hope, love
and apprehension. 

Al-Marroodhi said: I said to Abu ‘Abdullah – i.e., Imam
Ahmad: How many people there are who are praying for you.

I said: I fear that this is leading me step-by-step to my
ruin. Why do I deserve all of that? 

End quote from Taareekh al-Islam (18/76) 

Fifthly: 

One of the greatest signs that give rise to fear of being led
step-by-step byAllah to ruin and that Allah despises a person, is when Allah
grants him provision when he is disobeying Him and turning away from Him.

Allah, may He be exalted, says (interpretation of the
meaning):

“Those who
reject Our Ayat (proofs, evidences, verses, lessons, signs, revelations,
etc.), We shall gradually seize them with punishment in ways they perceive
not”

[al-A‘raaf 7:182]. 

Al-Qurtubi (may Allah have mercy on him) said: 

Ad-Dahhaak said: The more they disobey Us, the more blessings
We bestow on them. 

It was said to Dhu’n-Noon: What is most deceiving for a
person? 

He said: When he is given a life of ease with a lot of
blessings … 

It was narrated from ‘Uqbah ibn ‘Aamir, that the Prophet
(blessings and peace of Allah be upon him) said: If you see Allah giving
someone what he likes of worldly gains despite his disobedience of Him, then
this comes under the heading of leading him to ruin, step-by-step. Then the
Messenger of Allah (blessings and peace of Allah be upon him) recited the
words (interpretation of the meaning):

“So, when
they forgot (the warning) with which they had been reminded, We opened to
them the gates of every (pleasant) thing, until in the midst of their
enjoyment in that which they were given, all of a sudden, We took them to
punishment, and lo! They were plunged into destruction with deep regrets and
sorrows”

[al-An‘aam 6:44]. 

Narrated by Imam Ahmad (17311); classed as saheeh by al-Albaani
in Mishkaat al-Masaabeeh (no. 5201) 

Shaykh Ibn Baaz (may Allah have mercy on him) said: A person
may be tested with times of ease, such as abundant wealth, wives, children
and so on, but he should never think that this is a sign that he is loved by
Allah, if he is not obedient to Him. It may be that the one who is granted
that is loved by Him, or he may be hated by Him. It depends. Being loved by
Allah is not indicated by high status, numerous children, great wealth, high
status and so on; rather the sign of being loved by Allah is righteous
deeds, fear of Allah, turning to Him, and doing one’s duty towards Him. The
more a person fears Allah, the dearer he is to Allah. 

It was narrated from the Messenger of Allah (blessings and
peace of Allah be upon him) that he said: Allah grants worldly gain to those
whom He loves and those whom He does not love, but He does not grant faith
to anyone but those whom He loves. 

Narrated by al-Haakim (94), He classed it as saheeh, and
adh-Dhahabi agreed with him. 

Whoever is granted religious commitment is dear to Allah, but
whoever indulges in disbelief and sin, this is a sign that he is hated by
Allah, according to his situation. 

Moreover, it may be a test and a means of being led,
step-by-step, to ruin. A person may be tested with blessings so that he gets
carried away until he falls into evil, and ends up in a worse situation than
before. Allah, may He be exalted, says (interpretation of the meaning):

“Those who
reject Our Ayat (proofs, evidences, verses, lessons, signs, revelations,
etc.), We shall gradually seize them with punishment in ways they perceive
not.

And I respite them; certainly My Plan is strong”

[al-A‘raaf 7:182-183]. 

Or people may be tested with sickness, illness and so on, not
because Allah hates them, but in accordance with divine wisdom, so as to
raise them in status and erase their sins. 

End quote from Fataawa Ibn Baaz (7/147-148) 

And Allah knows best.