I can't do it', 'Maybe this is not for me'. Everytime we fail or make a mistake, we suddenly assume that we can never learn the job, or in the case of a skill, that we need to find a new skill to learn. We do this and let go of possibilities and opportunities that we could have reached in the field if we had just stayed back and tried again.
Remember when you were a child. You had to learn to walk, sit, read, speak, write, learn a new language, maybe even ride a bike. You went through all of that and learnt them. Of course, you probably failed on your first trial. But that didn't stop you....