Regret isn't always the most helpful thing, so it's not always advisable to look back at how you wish things could have/should have been. However, learning from mistakes, especially other people's mistakes, can be priceless.
There have been times in my adult life I've come to learn or realise things and then gotten a little upset no-one took the time to explain or teach whatever it was while I was young. Then, hopefully, I get over it and, if necessary, continue to learn/improve what I need to.
So the question is, what things/skills do you wish someone had taught you or taught you sooner, or maybe could have had help learning? And do you feel happy/comfortable in that area, and if so, do you have any recommendations/tips for others who have to learn the same thing?
EDIT - I was going to include my experience on this but I'm out of time so I'll have to add it later.