How can you tell if you are really set for the Marines? If it's for you?

I've been thinking about going to the Military after HS and have been looking at all branches but for some reason Marines have always caught my eye. I'm a junior now and I'm not really in all good shape now but am working on it though. I want to make a difference, be a part of something, do something with myself, fight, and to prove my past ex's I'm not a pu$$y that they thought I was lol.