I believe experiences shape your general personality more than genetics would, you know, that whole nurture over nature argument. Sure, there might be some little quirks you inherit that could alter your personality somewhat, but usually, it's the experiences that influence the way you act, think and feel. Negative experiences will impact upon your personality in a negative way, while positive experiences could change it for the better. It may also work vice versa too, although this happens much less often. I've had a few poor experiences that I could say have had a hand in changing my personality (such as being bullied in my younger years) which in turn has caused me to become snappier and more cynical, but also much less willing to take crap from people ever again. A few good experiences, such as meeting someone that I love and care about deeply, has helped me become more loving and considerate to others, especially those closest to me.