In this chapter Allamah Busairi R.A. mentions two reasons for restraining of lust and carnal desires.
Firstly: A person falls in love due to lust and carnal desires. After mentioning love in the first chapter he now mentions restraining lust and carnal desires. He also mentions that his entire life has been spent in sin. He sincerely regrets what he has done and repents to ALLAAH TA'AALA.
Secondly: Restraining lust and carnal desires is essential for gaining love for RASULULLAAH (SUBHANALLAAH) SallALLAAHU 'Alayhi Wa Sallaam. The love which has for Rasulullah SallALLAAHU (SUBHANALLAAH) 'Alayhi Wa Sallaam, is a pure love and can only be attained by purifying oneself of lust and carnal desires.