Since very young, behaving this way makes him feel secure

 

His mind gains a focus, and the pressure from the parents is fended off: see Mom, I'm not slacking, see how serious I am?

Overtime it became a reflex: to be unhappy in order to feel secure.

He needs to validate himself: I'm good enough, rather than looking outward for validation.

Love oneself before he can truely love anyone else.