I think this is the biggest take away. Feeling "behind" is always relative your goal. The feeling is also influenced by a "success bias" in which the examples/role models you see or hear about are the successful ones. Yes, compared to where Bill Gates was at your same age you're probably behind - but what about the other countless number of people your age with similar goals? How do you stack up to them? That should be your real metric rather than the 1 in a million success stories.
I agree in that regret is a useful emotion. But only as, as you said, a tool for evaluation and recalculation. Personally I believe it is better to make decisions based on asking your self "if I do/don't do x, will I be closer or further from my goals?" rather than making decisions based on "oh man if I only did x or y 10 years ago I would be where I want to be".
I think it can nicely be summed up with:
"The best time to plant a tree was 20 years ago. The second best time is now."
also - I know it's become a bit of a meme at this point, but "pivoting" or changing your goals isn't as bad of a thing as people make it out to be. I don't find there is anything wrong with re-evaluating and changing future goals based on progress and failure. I find it's better to change your goal based on a previous failure rather than give up completely or become stuck in the paralyzing regret phase.
I disagree with that. Most people are not successful, so if your target is the average, you are aiming at a data point that represents lack of success. It is important to understand that most successful people are not normal, and the higher the level of success, the less normal they are.
> "The best time to plant a tree was 20 years ago. The second best time is now."