Could anyone be the same after an experience like this?

I have seen this movie years ago and recently bought the DVD. I am not sure if anyone can be the same person after going through an experience like this. That is like when I was a kid and thought that anyone who had a smile was nice and caring. Then I met fake people who I thought were my friends who did me so wrong even though I was so kind and caring to them. So now I really do not trust anybody unless they go out of their way for years to do something nice for me without me asking. I can honestly say that I am a good person who will help anyone without anything in return. So I am totally confused at all of the back stabbers out there. Then again I grew up overseas as my dad was in the US Army so maybe I didn't grow up with the American way of stepping on people for your own gain.