Why do nice people always get hurt???

I consider myself a nice person. I'm not fake, I'm not judgemental and I truly do care about other peoples feelings! Well being nice seems to get me nowhere. All it has done lately is get me taken advantage of and got my feelings hurt pretty bad. Maybe I need to learn to have "thicker skin" and not be so nice. It seems like people like that don't get hurt nearly as often, because they know how to blow people off when they are being mean. They also know how to tell people NO, so that people don't take advantage of them all the time. For everyone out there who is nice like me I hope this works out better for you than it does for me, and for everyone who knows how to have that "thicker skin" and not let people get to them I could use a few pointers!