The best way to let go of the past is to focus your time and energy on the present.
The best way to let go of the past is to focus on the present, not only so that you don't have time to dwell on the past, but also so that you can lay a good foundation for the future.
But letting go of the past doesn't mean forgetting the mistakes of the past. It is important to learn from the mistakes made in the past. So that you don't make similar mistakes in the future.