What are you afraid of?
Sometimes God will command you to do something beyond your comfort zone. It will be hard, there will be doubts, there will be anxieties, and you may be afraid, and that's okay.
Let me remind you that you are only human, it is normal to feel these kinds of things. But also be reminded that God is with you, and he will not call you into something where His glory will not be seen.
God's power flourishes more on things that can only be accomplished through Him, for that is when we could see clearly God's hand.
So, when God asks you to do something, do it!
Trust Him.... even if all you can see are mountains after mountains.
Trust Him... He is bigger than what you are facing.
Trust Him... for he already saw your future, he is making it happen, and it is surely good.