It doesn’t matter what they think.
It doesn’t matter if they’ve discounted you or written you off.
It doesn’t matter if they believe in you or the dream that God placed in your heart.
All that matters is whether or not God called you to do it. If He did, if He gave you that dream, them go for it with everything that is within you.
Don’t listen to them. Don’t listen to the enemy. Don’t listen to your own self-doubt. Just listen to your all-powerfull, all-knowing, heavenly Father and start doing it.