I'm scared about how far I will let myself go in heated moments, as in, hurting the people I love...
I'm scared about how far I push certain limits, and scared about how much power we all have as people, which could be definitely be used for negative purposes.
I have been in heaps of situations where my actions could have directly and ultimately influenced another's to the point of them damaging their life...so far I've always done the right thing...
So yeah - I guess in some ways I'm afraid of aspects of my personality which I feel are less controllable than others, but I think being afraid is better than being unaware of the consequences my actions can have - and hence perhaps not realising that I am using them negatively. Writing - whether fiction or in my diary - definitely helps me become cognizant of these things.