J.E.
My kids are now 16 and 14. I thoroughly enjoyed when they were little. I still vividly remember holding my daughter and relishing the moments knowing it wouldn't last forever. Firsts are always fun and knowing with my second that it was the last time there would be "firsts" was a little sad sometimes.
When my daughter was in kindergarten and my son was in second grade we were having a discussion about school at the dinner table. They were talking about something that had happened and I had this moment where I realized they "together" had this life independent of me that they were sharing together. It was the moment I realized they really were growing up and becoming people, not just MY babies.
I do enjoy the freedom of being able to pick up and go somewhere last minute or that they can cook for themselves - daughter is a good cook and my son just discovered grilling.
I discovered my life had come full circle when my daughter was making pumpkin bars with cream cheese frosting and gave my girlfriend and I each a beater to lick. lol
Enjoy each stage of their lives. Teenagers can be a lot of fun. Kids are challenging at every stage in some ways, just enjoy them.