Why do people with good hearts get hurt the most?

I've wasted so much of my life and time doing the right things for the wrong people. Finally realized that all these years I should have been spending time on my life and my dreams. It's sad how people take advantage of people with good hearts.Too many chances, gifts, talents and opportunities wasted. It kills me when I think what I could've been and done if I spent all these years on me. I would definitely be more successful and not filled with stress, regrets and depression. I see young kids doing what I wanted and should've done when I was younger. I turn 30 next month and still far behind in life. I am trying my best to move forward, but sometimes I feel why bother. I'll keep pushing though, 1 step at a time. I turned the cold shoulder to many people who've done wrong by me. I've been told that I changed and have become mean. In my head I'm like NO! I just started taking control of my life and refuse to let people step over me again. I want people who like me for who I am and not what I can do for them. My issue is I often made myself too reliable. That is going to change.