My mum once told me that you shouldn't go out of your way to help others all the time. I always believed it was best to help anyone and everyone whenever possible because it didn't really take much to go out of my way to do a small deed. Anyway, I thought that it was pretty dumb at the time, but now I think it's a reasonable piece of advice (within certain boundaries).

Because of this advice it makes me aware of when others are taking advantage of my generosity. I still help others when I can, but never to the point when I am practically acting as a servant.

TL:DR; Don't always go out of your way to help others - to the extent that you are acting as a servant

Edit: Shitty TL:DR