Oh man, I agree with everything the first post said (which is the only post I read in this thread). I haven't been in a relationship for a year and before that one I wasn't in one for like 5 years. And honestly I don't miss it. It just seems like a responsibility I can do without. It feels like work exactly as OP said. It might be a side effect of my general responsibility-avoiding carefree attitude (it's a bad trait, I know) but I don't seem to like anything that being in a relationship entails. Especially the fact that you have to talk to each other all the time. All the texting and stuff... I'm not very asocial but when I'm alone at home I want to be alone at home. I don't want to text and let her know what I've been doing, what I'm doing and what I'm planning to do all the time. And listening to her side of things.
One good thing I've had in a relationship is, of course, being in love. Happened only once to me. And I don't mean just hugging and kissing and having sex. Though love can be quite poisonous as well if you aren't in love with the right person. Being in love changes you and makes you do things that you wouldn't do otherwise. You feel like you can move mountains if you try hard enough for her. You can sacrifice things and completely change your life plans and find yourself in a position your pre-in-love self would feel miserable in. And once the love fades you can get stuck in it. Too much love is the worst thing that can happen to a person. I'd rather be celibate than to go through that shit again.
Everyone wants what they don't have. My philosophy regarding relationships is now simple after being treated like shit last time: if you fuck someone over, you are loved, and if you are loved then you probably fucked her over. I got treated like shit and I loved her more. She left me for a guy who was an absolute shit towards her. When I treated my partner badly (wasn't aware of it at the time and not proud of it) they seemed to love me more. Worse you act towards someone, more they seem to want you. It all boils down to this. We all want we don't have and if someone seems more difficult to reach, we want her more. Relationships are a headache. It feels like trying to balance the most wiggly pair of scales ever. If you tip it too much to the right, she leaves you. If you tip it too much to the left you don't love her anymore.
We all love to tell ourselves that we are such a nice guy and the other guy she left us for is such a dick. But I've been both the dick and the nice guy in different scenarios and I can say it has nothing to do with being nice or an asshole. It's about either being unreachable enough to be desirable or being a doll with strings for the other person. What I said in the above paragraph goes for all relationships. Hell, it goes for all our wants, desires and vices on this Earth.