How many times have you thought you were too damaged, too screwed up or had too messy of a past to be used by God? For me, that answer is more than I can count. But just as clay is the potter's material, we're God's material. He is shaping us, even our past, into what He wants us to be.
A cracked pot has more places for the light to shine through.
Jeremiah 18:4-6
And the vessel that he was making from clay was spoiled in the hand of the potter; so he made it over, reworking it into another vessel as it seemed good to the potter to make it. Then the word of the Lord came to me: O house of Israel, can I not do with you as this potter does? says the Lord. Behold, as the clay is in the potter's hand, so are you in My hand, O house of Israel.