I'd marry my best friend... except she got a hole last week and I need to get it patched before we exchange vows.

Forget disposable relationships, it's the future man, we have inflatable relationships!
Insane Platypus said:
Loneliness is just a part of being human. We are social creatures but we are also individual creatures - we don't live in a hive mind.
Just to carry this line of thinking further. It's my belief that because all of us only ever truly know what's going on in our own heads, that our lives are spent trying to bridge that gap.
There are many examples in science-fiction of supposed races of creatures who live with joined minds so that everyone is connected, mentally, across an entire species. Human beings spend their lives prisoners within the confines of their own heads and thus, their own thoughts.
It's my observation that an overwhelming majority of all human behaviour is driven towards doing things to ease a deeper unbearable loneliness that we all feel inside; from the cradle to the grave, all we are ever doing is trying to find some connection to the rest of humanity and the universe. Even behaviour that seems self-serving like the accumulation of wealth (in the belief that wealth will somehow gain us respect and allow you to buy love and happiness), or behaviour that is self-defeating like suicide or self-mutilation (suicide to end the loneliness, hurting yourself to draw attention to other problems).
This is a problem to which there is no solution. Instead our search for an answer or a miracle fix-it-all is, I believe, what causes most of the interpersonal and relationship problems in our lives. Instead of accepting that ultimate loneliness is part of the human condition, we expect that we'll find some partner who will alleviate this; the greatest and deepest of all human needs. Rather than looking for a cure to loneliness, the best and most we can ever hope for is a kindred spirit to share the journey with.
My point is I see too many people, single or otherwise, getting into relationships for the wrong reasons, or expecting the wrong things from the relationships that they're in. Remember this: patience will always bring better results than desperation, and the loneliest moments of your life will not be spent alone.