"You're a big sister, aren't you?"

I suppose I make it pretty obvious that I'm a nice person. I smile a lot, I enjoy taking care of people. I cook dinners, clean houses, buy little gifts and remember how people take their tea and coffee.
You know how they say that "nice guys finish last?". Well, sometimes I wonder if nice girls even get to take part in the race. I'm not suggesting that I'm going to turn into a total rabid bitch, but I do feel like it might be time to stop being so bloody nice all the time.
A woman (ok, ok, a nurse) I spoke to yesterday guessed that it had to do with me being a big sister, that we automatically become a litle bit too caring at our own expense. I'm not sure this is correct, but I do know that I suffer from good girl-syndrome big time. The grades, the niceness, the caring, the way I automatically find myself in the kitchen cleaning up at family events.... And also the way I have put myself in situations where I know with 100% certainty I shouldn't be, just to "rebel" against my own nice girl-persona.
Well. New year resolution 2013, as overrated and pointless it may be, I'm going to be even kinder.
To myself.
The rest of you, well, you're just going to have to get by on your own. Unless I really, really like you, in which case I will probably to super nice to you. Cause, you know. I'm not a total dick.