What about if the promise is broken after you accept the promise ring?
If you break the promise of a purity ring, then naturally, you'll probably feel at least somewhat guilty. God will not be mad at you, though. He understands you and knows your heart. He adores you and is quick to forgive you. There's nothing you could ever do to sever His unconditional love for you. Although you may feel a little distant from God for a short time, a broken promise doesn't mean a broken relationship. You're still His beloved child. Besides, even if you break the promise and have premarital sex, it doesn't mean you have to completely let go of that promise. You can still try to do your best to remain chaste, if you so desire.
No matter what, just know that God will always welcome you with open arms and a warm embrace.
God bless you.