Hazrat Shaikh Moulana Muhammad Zakariyya (rahmatullahi ‘alaih) once mentioned:

Nowadays, due to people being physically weak, they are not instructed to engage in strenuous types of spiritual exercises. During my youth, I recall having seen many of our pious, saintly personalities engaging in mujaahadah and spiritual exercises. At present, on account of people being unable to manage such mujaahadah and spiritual exercises, they are asked to strengthen their hearts and protect them from all types of sins and spiritual maladies. In this way they will be able to acquire the same benefit. Therefore at all times one should safeguard his heart against sins and not allow it to wander astray. (Malfoozaate Hazrat Shaikh 1/110)

Source: Ihyaauddeen.co.za