This is an interesting and scary prospect of life. Honestly though I don't think that anyone will grow up alone and especially the wonderful people of this community. I may not be a good person to ask about being alone. I guess I'm one of those lucky ones who found someone, we clicked, and it just feels right. I think that will happen to most people eventually. I know that you can't go out looking for love and as people mentioned earlier, it will happen when you least expect it.
I also agree with widow that even if you are with someone you can have the fear of being alone. Mine is "What if something happened to jj? What would I do?" Other people think "I've been with this person so long, I don't know how I would live without them."
My mom is in a relationship like the latter. I don't think they are in love anymore and I don't think that they have been for many years. They stay together for 2 reasons. 1) My mom doesn't want to be alone. 2) My dad doesn't make enough money to support himself. I think that I were in this situation, in fact I know that if I were in this situation, I would rather be alone. Why spend your time with someone you don't really like for fear of being alone?
I think that many people have these worries and once you find the person you mesh with, you sill have other life worries. I hate to make reference to a Sex and the City episode, but it's running through my head. There is an episode where the women are at a party. Miranda gets asked if there is anyone special in her life and if she plans on getting married because being alone is not a 'good' thing. It bothers her and she is scared of being alone. Then she runs into one of the 'lucky' women who are married. This woman tries to defend why she isn't having kids.
Life is full of what ifs and fears. You have to keep on going with the belief that everything is going to work out the way it is supposed to. You are young and your life will turn out exactly how it's supposed to. And honestly, from what I've seen and read, you're not going to end up alone.
Oh yea, and this idea of "the one" is not correct. A person can have many loves and you can't second guess yourself for ending a relationship. If you put a lot of thought in the break up, you should have no regrets.