Ref: http://www.madeenah.com/feeling-a-weakness-in-imaan/

Feeling a weakness of Imaan – Shaykh Ibn Uthaymeen advises.

QUESTION: There is a question relating to a weakness [in ones Imaan], what are its causes and cures?

Sometimes a person feels a weakness in his religion.

RESPONSE: It is not possible for a person to remain on one constant level [of Imaan].

Even the Companions (may Allaah be pleased with them), they said:

“O Messenger of Allaah, when we are with you we take from your admonishment and we have Imaan, and yet when we return to our families – our women and children – then we forget.”

The Prophet (sal Allaahu alayhi wa sallam) replied,

“An hour for this (i.e. when your Imaan is strong) and an hour for that (i.e. when your Imaan is weaker)”

It is not possible for a person to remain on one constant [level of Imaan], but he should make sure his heart is rectified; if the heart is rectified then his whole body will also become rectified. A person should:

1. Leave off entering into matters which do not concern him
2. Leave off arguing and debating in matters that there is no benefit in
3. Leave of partisanship (tahazzub) – which has divided the Ummah
4. Turn to Allaah – the Exalted and Majestic

For this reason, you will see a common Muslim is better in his belief and sincerity than many among the students of knowledge, because many of the students are only [concerned with]:

1 Reading and refuting
2. Hearsay
3. What do you say, O so and so
4. What do you say about such a book, or so and so,
5. What has so and so person written

This is what wastes a slave, and takes his heart away from Allaah (the Exalted and Majestic), and the only concern he then has is Qeel wa Qaal (hearsay).

So my advice for every person, is that he should turn to Allaah (the Exalted and Majestic), and leave the people and their differing. This is the best thing.