I can help out here. Here are a few:

— External locus of control

— Habits

— Pleasure/Pain Balance

— Too much stress

— Lack of momentum

— Inefficient energy management

— Circadian rhythm out of whack (e.g. not enough sunlight; inconsistent sleep schedule)

— Lack of sleep

— Poor nutrition

— Lack of time management skills

— Lack of prioritization skills

— Lack of decision making skills

This is not extensive and it doesn't even cover people with mental disorders, on the spectrum, or battling life's circumstances (lack of housing and food, for example).

Just going with "be disciplined" without any context and understanding is like going to a car mechanic and getting "just have a working car". Very helpful!