As I read and then listened to the Gospel today I was again struck my Mary's fiat that changed the whole world. She lived her whole life forming her will to that of the Father's and she succeeded. Some say Mary being chosen was a reward for good behavior on her part and while that's true ion some level, her being chosen was a gift. A gift to her and a gift to us, for without her fiat where would we be?
"Let it be done according to your will." How often do we say those words and then take them back because of fear, discomfort, or laziness? It is so often a matter of making sure our feelings do not get in the way and our desires of the flesh or the world do not overcome us. That is what it takes to allow God's will to become our own. Or we try to bargain for a better time. Mary didn't say, "Yes, but can you wait until Joseph and I get married so it doesn't look so bad?" She said "yes" and trusted in God for the details.
It is believing and acting on the belief that God gives us what we need to do what he wants to do. We must be disciplined and vigilant, willing to be uncomfortable if necessary, knowing that in the end, saying "yes" to God's plan is the only way to thank him.