I can see that some of you are pushing yourself over your own comfort zone and achieving something new. But definitely we all will feel fearful when doing new stunts/tumbling. Fear is the last thing you can have because it hinders you from doing anything right.
A summarized paragraph from www.trickstutorials.com:
Fear is a natural emotion, a survival instinct. It indicates that you should be alert. Fighting or forcing away fear creates a counter force that will make you tense and anxious. This will interfere with your chances of landing a back flip (or perfecting other stunts). You need to release or forget the fear, not fight it. Fighting fear will only backfire. You'll be ready when you're ready. My advice for overcoming fear of this move or any other move is to do three things.
1) Learn the technique of the move. Visualize yourself doing it with perfect, flawless technique. Feel it, and understand it COMPLETELY!
2) Rationalize it. What is the worst thing that can happen? How could this bad thing happen? Why am I scared? You'll realize the worst that could happen is a small crash. You're scared of pain, and pain is irreverent. It will correct you so you won't make the same mistake again. Having a spotter will minimize the chances of experiencing a painful crash to a great extent.
3) Have fun. If you're having to force the learning process of the move you won't get it. When I was learning it the first few crashes weren't too fun. Then I let go of the desire to land the move and just started focusing on what is important: The technique, the thrill, and the moment. I can't release your fear, you have to do it yourself. Stop being frustrated and focus on fun.
I hope this would help some of you breakthrough from the fear of certain stunts/tumbling, let's all work hard towards the goal we want to achieve. Giving up because of fear is an excuse. Work hard Blazers! :>