If we accept the fact that we can't do something, or it's too hard, then we've set ourself a limit.
I never thought I'd be able to do a chin up and just accepted it. One day as a joke, I got my brother to boost me up and help me do one, but then realized I was actually pretty close to doing it by myself.
Since that moment I removed all doubt and realized I am capable to achieve more than the limits I place on myself.
Who actually says it's too hard? Or is it a thought we've just created that's driving us? After all, they did put a man on the moon!