You’ll Only Ever Be As Good As You Believe You Can Be
There are cases where it is good to be wrong and cases where you believe that there is something that you can't do. It's all nonsense ideas that you got from others, probably in childhood where we get most of our beliefs, or something wrong that you assumed at a particular time in the past because you didn't know better at the time.
If we sit down and identify what is holding us back, what caused it and recognize that it's just a false idea that we had at a certain moment we can change it with a more positive belief and so change the outcome of our lives.
It doesn't matter so much where those beliefs came from, the most important thing is to recognize and change them so that from now on things will be better for you. As I said, the best thing about beliefs is that they aren't fixed, they can be changed anytime. You just have to decide how you want things to be from now on and believe in yourself.