What is past is past. Similarly, there is no point in feeling sad about unpleasant things that happened in the past. You can't change or correct the past. It's just like making a film. You cannot correct anything once it appears on the screen.
Life is also like that.
I believe those who bask in past glory are fools. Of course, we may think about certain incidents or people that have touched us. I'll never, for instance, be able to write a book about my past experiences. But the world is full of people who are nostalgic. Whatever happened yesterday is beautiful for several people.