Feeling useless?

I've been in the same situation, and the best answer I can come up with is, "You can't help everyone"--some people just need to help themselves by changing their outlook on their situation. I have a friend who is depressed, and I tried to help him. He ended up snapping at me. For days I felt guilty and confused. I was only trying to help, and now I didn't know how to confront him. It took time for me to come to terms. He probably didn't even want my help--I just knew I wanted to reach out and help because I can't see him sad. This is why you have to be cautious helping someone. It might bring you down with them (a reason why I try to have more positive friends). So, this isn't your fault. Some people just can't be helped. At least not by you or by me. So just stay positive and happy :) There will be a time where your help is needed, welcome, and appreciated.

The question is: if you don't succeed in "changing" someone, do you consider all your efforts wasted? If you look at giving as a gift, a gift you don't want anything back for, lack of concrete results may bother you less. It's fine to set limits to how much you are willing to give like this, and to look to pursue helping other people that make you feel more accomplished.