What would you do if you found out that special someone you wanted to spend the rest of your life with with doesn't exist such those you were interested in or attracted to would never be attracted back to you etc? You could have somebody however it wouldn't be anybody that interest you and that situation was to last for the rest of your life.
I would never ever think like that. In fact just thinking like that would make me live like that.
I'm a realist, believe me, but optimism goes a long way. You're probably tired of hearing self-confidence and stuff, but in reality if you show the right amount of proper confidence, you could get anyone. And if someone doesn't want to be with you, it's their loss! Don't get bogged down by it.
I may be 18, and you may be much older than me, but frankly it's the fact of life. Don't get lost in your emotions.