Justification?

If the end justifies the means then why do the means not justify the end? Meaning if someone does a lot of horrible things and gets good results and that is okay, why is it not okay if someone does a lot of good things, with good intentions, and it ends badly?

I had nothing but good intentions, and what I thought were good actions. No matter what I do, and how good my intentions are, I always seem to make everything worse. Sometimes I wonder why try? If everything is going to end up worse anyways how necessary is my involvement? That train of thought always leads to this: How much worse would things have turned out if I hadn't gotten involved? Is it worse to do nothing, or try your hardest to do right by someone and fail them?

I try my best, as I feel everyone should, to do right by everyone. It seems to me that everyone I come into contact with is worse off because of it. I just want to touch people, to change peoples lives in a way that other people have helped me change mine.