For me it can have a huge effect. Sitting down and thinking of all the "stupid" things I did when manic can cause me to slump right down. I end up hating myself soooooo much and begin to make the issues bigger, convincing myself that no one will ever forgive me or love me again as I curl up further and further under the duvet....

It's easy to say "let go of the past" but what is done is done, forgive yourself, move on. Advice I'm trying to learn to accept myself!