Write while the heat is in you. The writer who postpones the recording of his thoughts uses an iron which has cooled to burn a hole with. He cannot inflame the minds of his audience. - Henry David Thoreau
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.