You know, that's a good question, and one that I don't think can have any one specific answer. Like Sannah had mentioned, everyone is unique, making the problem and solution equally unique.
Byz also has a good point, fear of removal from the comfy zone can be a common reason for many.

It would seem that since we grow accustom to what is familiar to us, we have a tendency to accept that as how it's supposed to be, despite the fact that we sense or even are fully aware that how we behave isn't healthy for us.

Acknowledging that there might be a problem is the first step. The hard part is applying change to our OWN behavior. Some can do with without seeking assistance, while many may not have that ability and need to seek help.

Alot has to do with the surroundings, (and occurrences) during our upbringing. That is what develops our structure for adulthood. For me, because I was a part of such a huge family, we seldom received much individual direction, although it was not abusive, it was still a structure that lacked much individualized attention, which I perfectly understand now. I'm aware of it, yet breaking the cycle that is a result of it is the hard part.
It takes constant attendance and self-forgiveness, until a new pattern of thought can be applied to a newly constructed behavior pattern...for me, anyway.

....Something like that, I think....lol.

Shangrala