I feel like any time I spend a lot of time with married friends (which isn't that often, because our lifestyles are so different now), I see the downsides of married life, and even a bit of jealousy on their parts that I am single and free. So, I recommend doing something awesome that married people/parents can't do, like a last-minute trip overseas or eating nachos in bed and then farting for half an hour, then go hang out with your married friends and talk about it, and watch how jealous they get.
Also, I've not read this book, but I heard it reviewed on a podcast and it's very intriguing:
http://www.amazon.com/Going-Solo-Ext.../dp/0143122770