We all have regrets and most won't hold us back. In letting go we acknowledge a lesson learnt and maybe feel a bit guilty or annoyed that we didn't see the problem at the time - hind-sight is an annoying teacher. Give your past self some credit - they weren't as wise as you are now!
If you’re regretting past errors or fear repeating them, try to move on. The past is most definitely not a guide to the future but your successes might be!
Not all your IDEAs will succeed. Move on and create some more. Which sounds like classic advice for entrepreneurs…
“How to Stop Holding on to Things And Truly Live” by Vishal Kataria https://link.medium.com/BLAb4FLBeW (paywall, sorry)
Winnie-the-Pooh has an interesting if poignant perspective on this - at the end of A. A. Milne's original version Pooh and Christopher Robin walk off to 'the enchanted place, and there we leave them'. Which is a statement about the end of childhood, leaving it behind but not forgetting it. It is now done, but still exists - we've learnt from it but are moving on, can't revisit (arguably shouldn't try).
How swiftly the strained honey of afternoon light flows into darkness
and the closed bud shrugs off its special mystery in order to break into blossom:
as if what exists, exists so that it can be lost and become precious.