Compassion...not

Why is it that every time I try to be nice and help somebody else i get in trouble for it? someone needs paper- I to give it to them. someone forgot lunch money-if i have it to spare, i give it to them. some one needs to use a phone- Im nice enough to let them use mine. However when a friend(supposed to be Best friend) borrows your phone and leaves school with it. Im supposed to just accept that? I dont think so!!! I'm all for the whole Compassion thing ,but that took it just a little too far.