Betting on your beliefs is a great way to see how well calibrated to reality you are and keep a record of your beliefs. It's easy to forget all the mistakes you've made, but bets help you remember those mistakes and learn from them. It doesn't even have to be real money, you could also use Manifold or Metaculus to accomplish the same end. 

 What I do is I don't write anything down, I promptly forget every wrong prediction, and then when I look back I have 100% accuracy.  I feel great and learn nothing.