why are two natures so important?

St Gregory the Great tells us about Jesus being fully God and fully man today in A Year with the Church Fathers.

He says that it's very important that we remember both natures of Jesus... fully God and fully man. And part of the reason that we should remember that is because it is a perfect picture of what God does in our lives each day.

Frederick Buechner is one of the best authors I've ever read at showing the perfection of God meeting the imperfection of man, and what that looks like. And that's what we need every day, right? We need God in His perfection to reach down into our messy, imperfect human lives and help us to be better. Help us be more like Him.

There is something in us that makes us uncomfortable with this. Something that wants the holy to stay over there, and the sinful to stay over here. But that's not how God works. God puts His holy hands into our dirty lives, and His holiness is more powerful than our dirtiness, so He affects us in a powerful way.

God, please work in our dirty lives and help us to be like You... a meeting of the eternal and the temporal.