Let it go. Move on. Live in the moment. These are valid sentiments — words of wisdom that are featured in self-help books and spoken by personal development gurus. And I honestly adhere to those notions; moving forward from certain chapters and releasing old ghosts is freeing. And healthy. Staying present encourages appreciation, of beauty, of the little things.
However, without discounting the aforementioned points, I propose that the past is immensely valuable as well. Happiness could be attained via reminiscence, and in the past, meaning could be garnered and lessons can be learned.