Hadhrat Shaykh Masihullah Khan (may Allah have mercy on him) said,

“Those treading the Path should strive to follow the method of Messenger of Allah (Allah bless him and give him peace) in everything.

Following the Sunna creates much light (nur) in the heart.

The Path to Perfection, page 121

This light (nur) makes it possible to differentiate between virtuous and sinful easy.  It also facilitates performance of virtuous and abstinence from sin.