When I compare myself to my friends who are married I honestly think that I am at least as happy as they are, if not more so.
Of course there are things I would like to have that I do not, like sex, affection, a constant partner in crime, someone always available to go on holiday with, someone to cheer me up after a bad day at work.
But the freedom I have to do all the things I enjoy, the time and space to develop really fabulous friendships, knowing that my house and lifestyle are the result of my hard work alone, ability to be spontaneous and do whatever I want on a whim, are all very valuable to me and I'm getting to the point where I no longer long to meet a life partner because my life is very nice as it is.
eBear makes a good point. A good selection of friends makes a huge difference. I have plenty of general friends who I socialise with, have dinner parties with etc. but I've noticed that my good friends fulfill different needs. I have my holiday friend, advice friend, cosy evenings with board games friends, days out friend, walk and coffee friend, bike rides friend, friends I do my hobby with etc. etc. All of these are friends I also do general eating/drinking/having fun with but between them they all fulfill various needs without anyone of them being aware of that or being under pressure to make up for the fact I don't have a partner.