Have you ever received an honor and then realized the responsibilities that come with that? I can't imagine being elected president -- it'd be amazing for 30 seconds, and then the pressure of dealing with so much power and so many people would come crashing in. It'd be overwhelming. I see the news constantly updating the salaries that sports coaches make, and then I watch press conferences where every action is criticized and see how they have to deal with recruiting year round and it seems like every week there is some new crisis. It's hard.
Mary is put in an incredible role through this honor... but notice how God will take up the action. The responsibility falls to God, and so Mary doesn't have to be flawless. Mary doesn't have to be perfect. She simply has to say yes to what God is going to do in and through her life.
The same is true for you. You don't have to be perfect and flawless and perform under pressure. You simply open the door of your heart upon which Christ is already knocking, and say yes to the things God wants to do in and through you. God loves you and is at work through the power of the Holy Spirit. Trust in God.