I'm definitely a positive person. I think it's because I have no expectations of anyone doing anything for me, so I'm always surprised and thrilled about the little things.
As far as letting things roll off my back. I learned early on not to take things personally. I try to live my life true to who I am,to give more than I take, to remember that you can be honest without being cruel to think of others before taking action, to focus on fun/laughter/creating good memories, and to be a positive force; so that seems to reflect back to me. (and by the way this is what I think is the true meaning of karma - a reflection back of what you give out - not that a bad thing is going to happen to you, because you wronged me that so many people refer to)
Yeah, occasionally people will be nasty, or have negative energy, but when I run into someone like that, I figure it's because they are dealing with something going on in their life, and probably has very little to do with me. So I accept it as that. As a matter of fact, when I run into someone like that I'll usually go out of my way to see if there is something I can do for them to make it easier for them. Sometimes when you lighten someones load just a little bit, it makes all the difference in the world.