One of the top 3 best decisions I've ever made was deciding to wrestle in high school. Practice literally consists of being thrown to the ground and getting back up. It made me develop physical and mental strength that has aided me in all facets of life.

I imagine just about any martial art will do the same so long as it is sufficiently difficult (i.e. at times extremely unenjoyable) and that you stick with it no matter how much you want to quit. Of course it should be something that is usually a blast, but will routinely push you to your limits. Don't think about how you're building your toughness, just focus on the task at hand and what you're trying to accomplish in that precise moment.

Hope that helps