How can I stop being so ditzy?

This is a sad question, I know, but I need some advice on how to act more mature and less ditzy. I'm always full of energy and kind of reckelss i.e. "let's go play frisbee in the rain, or let's go rafting down the river in snow tubes even though it's only 50 degrees outside." I tend to say things that I regret, and I laugh at almost EVERYTHING. I guess what I'm really asking is what would you consider ditzy? I don't want to be dumb and annoying, but I also don't want to be super serious and boring.