Is it accurate to say that there is nothing we can "do" to prompt God's favor?

My pastor preached a message indicating that Mary prompted God's favor and that is why he chose her to be the Lord's mother.

I am having problems with this comment. My pastor said that Mary didn't prompt God's favor for her salvation, but that she prompted God's favor by her obedience and that we can choose to obey too (and as a result prompt God's favor toward us).

I do not look at either salvation or sanctification from this perspective. I believe we are saved by grace and that we grow by grace. I think this perspective is dangerous, but then there's the whole idea of "rewards" in heaven...

I am very interested in your thoughts.