Hadhrat Hakim al-umma Mawlana Ashraf ‘Ali Thanawi (may Allah ahve mercy on him) said,

“Hardship persists in performance of good deeds.  It is because these actions are against the desires of the lower self (nafs). The lower self essentially tries to fight them off. This  may be a minor or a major battle. Hence, it remains essential to act against the desires of the lower self by doing spiritual struggle (mujahida) life long.

This is true both for the novice (mubtadi) and the one who has arrived (muntahi). Both of them have to face the opposition of the lower self some time or another, either in  form of laziness in performance of good deeds or indulgence in a sin. Novice gets into it a lot and the muntahi a little. In order to prevail in this battle it is essential for both of them to engage in spiritual struggle (mujahida). ”

Basair al-Hakim al-Umma, page 164-5

Related: Spiritual struggle