That happens to people that get in a rut.
If you hang around your wife (or any woman) all the time, they'll get bored with you [Jennifer Hudson - Spotlight]. When you're not married, more than likely you're not living together and you still do cool and exciting things so she's not used to you being right there for it whenever SHE wants it. If you live together... those comedy show tickets turn into electric bill money, the nice dinner turns into the cable bill... then you're pretty much stuck in a house or apartment taking each other for granted. You have to remain interesting. You still have to stay fly and a little elusive kinda. Keep her interested. I know some dudes that get treated like kids and with no respect at all because their women is so used to them and they let themselves go kinda.
If you can still look nice to your woman... you'll get the same amount. The day you sit down and watch the game with 3 bratwursts and a a 40oz beside you with mustard on your shirt... it's a wrap.
When you have kids though... the kids will make her tired with laundry, cooking, homework, regular fun.... so you can forget about doin' the humpty dance for awhile, lol.
I'd be scared to be single with all ish floating around though. That's just me, I'm a hypochondriac.