What was your "should've, would've, could've"?

So long story short, I just re-kindled my relationship with my best friend whom I’ve always dearly loved through all these years but never really told her. We had a chat about it and she ended up saying “you should’ve told me because I felt the same”.

This is probably one of my biggest regrets. She was my “I should’ve, would’ve, could’ve”. What is yours?