& my weakness is, that i care too much

I'll just come out and say it, I'm depressed. My life is heading nowhere and it seems like when I get a step ahead, it is not long before life is forcing me two steps back. I feel worthless and like my efforts go unnoticed. I'm trying my hardest, and I'm failing. I worked so hard to get to the point where I was okay, and I was truly so happy, and now here I am back at square one. Everything has fallen apart, and I feel like I am in far too deep to fix it. I'm getting walked over and I feel like no one cares. I don't understand what more I can give. I don't understand why I am just never good enough. I know I am a good person, and I try my best to show people how much I care by giving and it has never failed to come back and bite me in the ass. I'm always a second choice and I'm so sick of it. I need to become the type of person who puts themselves first, and it's not me at all, but I have come to the point where I don't have any other options. I'm tired of being walked on, and not appreciated for my efforts. So honestly, from now on, if it doesn't benefit me, then to hell with it. I hate that I have to change who I am, but I can't keep feeling like this. It's not helping, and I don't know any other way to fix it. From here on out, it's all about me, and a few select people who have always been there for me/ supported me. There's a lot that I don't understand, but I'm truly baffled at the fact that the people who have the biggest hearts, who care the most and are down right amazing people are always the ones who get fucked over or lack the experiences they so greatly deserve. Why? Why must these people have to resort to turning into heartless bitches in order to get what they deserve? Why must they hurt and suffer the most? Why can they give everything they have, and continue to give until they have nothing left and they still come second? It's sad to me, and I wonder just how much I have to do or how far I have to go until I can get what I feel like I have deserved for a long time. I guess that's how life is, but if you ask me it's pretty damn unfair.