Going for the feeling without the actual downside? Play video games MMPRPGs. Shoot zombies until they finally overwhelm you. Shoot cops in vice city until the army comes after you. Jump out of helicopters.
I really liked therufs suggestion list below. The downside, the thing you are risking in each of these, doesn't actually harm you, it makes you stronger.
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.