Mental blocks were one of the things that held me back in gymnastics. Now, I'm 26, and still get them! It's normal. The root of it is just over thinking it. You worry about everything, and let the nerves take control. I recently just started gymnastics, after a 10+ year break, and when I start feeling a block come on, I just go. And I'm fine! I know it sounds like the easy way out, but if you do it on a skill with a coach, and realize you can do it, it gets easier and easier to get over the blocks. I hope this helps!