Okay, I am joining this conversation a little late...
But, first of all, James -- it seems like this relates to my issues...
You know them well.
I do not believe there is a "one" that you can be happy with. You can love many people throughout the course of your life. There are dozens of people who can make you happy and "complete" you, so to speak. I agree with the people who say it is all timing.
However, I am not a pessimist... I'm not saying that it's only timing and that relationships mean nothing and they only work just when they are convenient. I just think they you have to incorporate the best of both worlds... practicality of being with someone who is also ready for what you want (instead of forcing something with someone who isn't) and passion/emotions/etc...