In today's passage, God tells Jeremiah to go and watch an artist. There are no other instructions; just the implication that if Jeremiah pays attention he'll learn something. As the potter forms and reforms the clay, Jeremiah sees an image of God shaping our lives. The potter puts a part of himself into the art just as on a grander scale our creator God breathes his life-giving spirit into us. Isaiah 29:16 also uses this picture and adds an observation that when we question God it's more or less like a pot telling the potter that he doesn't know what he's doing. Isaiah doesn't necessarily tell us not to question God (Jeremiah sure does plenty of it in his book) but we probably shouldn't hold onto any illusions that we'll tell God something that he didn't already know. Which brings us to the question of whether we are just pawns in a big clockwork life or if we have free will to set our own destiny. All the commentaries label the potter and the clay as "the classical illustration of the divine sovereignty in relation to human freedom". Paul jumped into the fray in Romans 9 when he was asked how anyone could be responsible for his own sin if God the Potter's shaping was beyond our control. Like Jeremiah, Paul stated that God would do what he wanted to do whenever he wanted to do it. He'll show mercy, provide salvation, and allow tragic consequences and destruction to whomever he wants in total disregard to how we pots feel about who deserves reward or punishment. However, both Jeremiah (Chapter 31) and Paul (all over the place) insist that the law of God is written clearly on our hearts and we ignore it at great peril. We're not responsible for anything except obedience. But life is not intended to be a chore. It's tragic if "existence is a idle game and life a festival held for profit" (Wisdom of Solomon 15:7-17) and we're satisfied as clay shells not knowing the One who breathed a living spirit into us.
Irenaeus, a church father of the 2nd century explained it much better than I can. My paraphrase of his take on the potter and the clay:
If you are the work of God, await the hand of the Master, the Artist who fashions everything in due course. Keep your heart soft for Him, lest becoming hard, you lose the marks of His fingers. But should you be hardened and reject His artistic work, with your ingratitude you'll lose both His art and your life. For to make is the property of God, but to be made is that of man.