I regret a lot.
Sometimes I don't have much of a filter on my mouth, and I regret the things I say to someone. Like saying my best friend looked like "Amy Winehouse on crack" when we all had teased hair for something at school. I meant it completely as a joke but she got very upset by it and stopped awknowledging me for a week. Like, beyond not talking to me, but looking at me with a completely dead look in her eyes.
And then I regret the habit I developed over that week that took me half a year to break.
And I regret not having friends, and being generally antisocial my first two years of high school.
And I regret all of middle school (I really don't remember 3 years of my life, it's bad, I've completely blocked it out.)
And I regret being nasty to my mom and thinking ill thoughts because she can't help around the house anymore.
And there's more, but there's the tip of the iceberg.