What drives a person toward self-sabotage?

Nikol said:but, shy people always seem to be making excuses for themselves, constantly apologizing...

it basically boils down to the fact that self-humiliation isn't even a thing—it all just depends on how you perceive yourself

I actually think it's the other way around. Self-humiliation is very real. It’s impossible for someone to
actually belittle you unless you've already handed them the permission to do so—so, in that sense, there's no such thing as being "humiliated."

Is this just straight-up masochism?

It's mostly just FEAR. That’s the whole foundation right there.