I worry about my self confidence mostly for myself. While I may not worry about what others think about, I know this is how I want to feel. That's why I'm working out because while most of my costumes show my stomach and I do not by no means look bad, I still think I could do better. Not much more so in the toning. But at the same time you also have to love your body for what it is. I know I'm not 'fat' but I just feel there are ways I can better myself. This thought will vary from person to person. Some people are very happy with the way their bodies are and some are not. If you are not feeling good about your body for YOURSELF, then you can pick up a regimen and make yourself feel better! But if you are doing it because of what other people say on the internet, well then they need to reevaluate their lives if they are picking on people for how they look. What you need to remember is to do things FOR YOURSELF. Not for others. That's why a lot of my friends think I would look fine if I did my cosplays and while I agree it's not that bad, I still want to start a healthier lifestyle just as a personal quest.
So in short: Remember that you are beautiful for who you are, and not what some douche says on the internet. Think about what YOU want. And when you realize that, then you'll be a lot happier knowing you are who you want to be.