Friends come and go, you get new ones. My friends from high school are not the same people, and neither am I. We wouldn't get along the same any more.
My biggest regrets would be...
Not working harder. As a teacher I have the ability to really leave my mark on the world. While I try to reach every one of my students and inspire them, there is certainly more I could be doing.
Having more fun with my wife. It seems we get complacent after 25 years together. This is good in a way because we can just sit in silence and keep eachother company (hard to explain unless you've been married for 25 years). But I wish for more oportunity to sweep her off her feet and hear her laugh.
Lastly, sharing more of my experiences with my kids. Too often I leave the kids at home because I know at some point they'll get bored. But there are moments when I'm out fishing or four wheeling that I think, "Dang, my kids would have had a blast doing this."
All things to work on...