It is worth looking around to see if there are any single women or men you admire - I am lucky in that I know several, and so for me the idea of being alone doesn't seem so bad. Being in a relationship is no guarantee of having real companionship. Single people are not necessarily perverts or weird!
Although some friends do come and go - what are sometimes called 'friends of happenstance', the 'friends of the heart' do not, and I have friends I have had all my life, as well as those who have been friends for certain periods.
We know long term relationships are possible. But what about the possibility that we are enhanced as human beings by our ability to love widely as well as deeply. Another poster talked about 'scarcity' on Kimmerz's thread and I also wonder if this desire for an exclusive relationship is born out of that to some extent.
I really want to challenge the idea that relationships other than a one on one significant other are second best. Sometimes these are the best thing for us at certain stages of our lives, teaching us to have wider concerns, and grow parts of ourselves that actually get neglected in an intense one on one. To be fully present for people other than our significant other is a great gift to be given and to receive.
I was lucky, and married to a man from whom I learned a lot, but I have learned many others things being alone, and developing my friendship group to something that is emotionally very sustaining. Just a bit of food for thought here!