Sometimes a lot of failure can be easier to deal with than a little. Failing at something that you feel you “should” be able to do can have some sting to it. Failing at something that is downright “impossible” to do is expected and can thus seem less risky from a psychological or social perspective.
In our personal internal work we should definitely be releasing our limiting expectations of what we “should” and “should not” be able to do. However, sometimes it can be useful to have little mental tricks to push the envelope and make it easier to do things that we would not do otherwise. If you’re having a hard time with challenging yourself because of social or internal pressure it may be worth taking a large leap instead of a small one. Really dare yourself to perform something in a way that is well beyond what you feel are your capabilities now. No one, not even you, will expect you to succeed right away, so you have a built in tolerance for failure you can play with.
At the very least when you return to a more reasonably sized challenge, you may find your perspective has shifted and your abilities exceed your original assumptions.