In life you will find that some people are too busy for you, while they will make some time for you every once in a while, they will only fit you into their schedule when it is really convenient for them.
Ask yourself this when someone says you can't do it. What's holding you back? Exactly. Nothing but them and you, but only because you are letting them.
Dear Self. You know what they say about perfectionism...don't you? Why you don't have to be perfect, and in fact it's necessary that you don't try to be.