What's stopping you?

This summer, my son learned how to ride his bike without training wheels. At first he was terrified and he kept wanting to give up. My wife and I kept pushing him to fight through the fear and keep going. I recently started training in jiu jitsu. I'm sore all the time, and it's hard to keep getting my butt kicked class after class. But like all new things, you have to trust the process and just keep hammering. What's keeping you from doing what you want to do?