For a while, I thought nurture had a lot to do with it. Now that I have kids, I thought 'nature' - because they both seemed to be born with their own, very distinctive personalities. I called them my 'slot machine babies' because it seemed to be a pull of the slot handle - you get 3 cherries, 2 7's and an olive, whatever.... But now I really think it is a mixture of both nature and nuture. However, I remember feeling the way I feel about life from a very young age - call it my nature. But then I know the life I had growing up was a very strong influence - in my self-confidence, ability to trust, etc...
So to answer your question of what influenced my personality, I believe I was born with my personality, but then it was shaped by my environment and influences growing up. I hope I can provide the same for my kids - positive, nurturing and happy so they are self-confident and sensitive and intellectually curious.