Wish I could be more helpful but I only know one way to let go of regret, guilt, shame, demons, and baggage:
Stop caring.
Thats all. Just remind youself in the grand scheme of your life it really doesnt matter and there isnt shit you can do about it anyway.
IF there is something you could do to correct the situation then you need to try, otherwise it will eat a whole in your psyche until the day you die.
If it actually does matter in the scheme of your life but you cant do anything about it, then remind yourself it doesnt mean much in the grand scheme of the world and all your actions are utterly pointless to about 6 billion people.
I have no idea how George W Bush sleeps at night. He fucked up America real good and did a dirty deed to the rest of the world as well.
Also, as others have pointed out, there are literally about 1 million variables for which you cannot account and about 100,000 you cannot change. Dont worry about shit you have no knowledge of or power over. Its pointless and will just make you crazy.