Oh boy, do the Israelites slip up this week. They have just received the Ten Commandments, have heard God speak to them and have vowed to do all that God commands them, even if they do not fully understand why they must. Forty days later, they're dancing around a calf made of melted golden earrings and calling it a god! What happened?
Have you ever had a serious talk with your parents and vowed never to misbehave again? You will never pinch your sister again. You will never miss another homework assignment. The promise you make is a true one, made from the bottom of your heart. Two weeks later, you just can't take it anymore, and, whoops!
Keeping your promises, especially the important ones, is always an uphill battle. But don't give up. Wipe the slate clean, and start again.