Most of the love relationships are emotionally draining and require a daily effort once that the honey moon phase is over. There is nothing to envy about the married/attached people you know. They've got plenty of issues they're dealing with on a daily basis, some of them are even facing serious crises or simply learnt to reach a happy compromise. There are very few lucky people who haven't had to sacrifice something very important to them for a love realationship, and even less people who honestly think it was worth it.
You don't lack anything, Andrew, just the realisation that your life as a single guy is better than the life of many of those couples that make you feel insecure because their daily reality you actually don't know.