Growing up, one of my favorite games was the original Pokemon. I played red version for hundreds of hours.
There is a section of the game where you have to board the SS Anne, fight a bunch of trainers, collect the cut HM, and fight your rival. After you collect CUT and leave the ship, the ship sails away. And it never returns.
This is the only section of the game where you can never go back (without glitches).
I think about my time coming up. The things I've lost. But more importantly, the people I've lost. People who I've enjoyed their company and shared fond memories of. And unfortunately, the same people I would come to hate.
My hatred of them makes me feel regret.
If I had just been a little different back then, knew how to start a conversation, or just have had some extra charisma, or was willing to take more of a risk... maybe I wouldn't have come to hate these people.
Maybe the relationships with these people could have been sustained and become ... good.
But just like the sailor in Vermilion City says "The ship has set sail."