The grass is always greener, even if you find a good partner you have to put a lot of effort and attention to the relationship to keep it going well, also doing things you may not want to do but have to as its a two way street.

Then there are bad relationships, kids etc. It's all about tradeoffs. One thing I like about being single now (divorced) is I can do what I want when I want but also have socialisation when I want it. Would never go back to a live in relationship just too stifling. My adult daughter lives with me though so I have daily social time which, along with other family, friends, is enough for me (sometime too much and I have to decline).