Hakim al Umma Mawlana Ashraf Ali Thanvi (Allah have mercy on him) said,

‘The seekers must understand it upfront that the spiritual struggle (mujahida) is always needed (to abstain from sinful).  It is not that you do it for few days (in the beginning of the path). It is lifelong endeavor.

Understand it by an example. In sickness medicine and precautionary efforts are essential. After recovery precautionary methods are still needed. Moreover they are even more required in healthy state. This is because in sickness the body system is impaired, the sense of taste is changed and desire for different kinds of foods is itself diminished. In addition if the patient indulges in any food harmful he quickly feels their  side effects. Whereas in healthy state the body systems are stronger and therefore the side effects of indulgence in harmful is not immediately felt. Also there is a desire to eat. Therefore, more care has to be taken in healthy state to prevent a relapse.

The physician have stated that relapse of an illness is more severe than the original illness.’

Khutbaat e Hakeemul Ummat ra, volume 23, page 274