I actually got engaged when I was 22, and married when I was 23, so this is dead on intended for me. Here's the problem-- I can do any of these 23 things married or single ('make out with a stranger' may cause some issues, but that's not top on my personal to-do list anyway).
Some of the very strongest relationships I know are couples who met in college, or earlier. Of course I know some divorcees as well, but I don't think age has anything to do with it.
http://www.huffingtonpost.com/vanessa-elizabeth/23-things-to-do-instead-of-getting-engaged_b_4523117.html