Purification of soul and refinement of morality which are in fact exiting the dominance of Iblis and the rule of Satan is one of the greatest of deeds and the most essentials of wise acts [1]. If you open one door to the (inappropriate) wishes of the soul (inappropriate desires), maybe you will open many other doors. At one time, due to following (your own) soul, you will be inflicted with some evils and from there you will be inflicted with thousands until God forbid at the end, the road to the truth is blocked to you [2]. It is narrated from Imam Khomeini who said: If you take one step for attaining knowledge, you must take two steps for purification of the soul [3].
[1] Sharh Hadith Jonood wa Jahl, Imam Khomeini,Page 68.
[2] Sharh Chehel hadith, Page 171.
[3] Bardashthayee az Sireh Imam Khomeini,Vol. 3, page 186.
source : Shafaqna