I wanted to chime in so you know that these are very normal feelings. There is nothing wrong with you.
I met a girl who blew me off my feet. The world was entirely different place with her there. I learned so much about myself, my environment -- I grew so much as an individual.
She had the ability to challenge my jaded, ornery, stubborn ways. She was a perfect blend of intellectual; with career success to back it up; and care free hippy. She was fiercely independent; but occasionally, I would get a glimpse at her softer vulnerable side. Normally, I would hate leaving the house and prefer to work on my hobbies, projects, cars, etc. but with her, I wanted to go out. I wanted to explore the world, and I wanted to do so with her at my side.
I had been in a fair share of long term relationships; and I was no stranger to commitment. In each of those relationships, I figured I would marry the girl. Not because it felt 'right'; just because... that's eventually what you do, right? With this girl I KNEW.
I used to roll my eyes at the whole "when you know, you'll know" or "you will just know", when asking about how do you know if a particular individual is who you are to wind up with. But with her I KNEW.
In fact, I have never been so positive, so sure, about anything in my life. So naturally, when it didn't work out (I moved to California, things faded...), I was particularly devastated. The only thing I was absolutely 100% sure of in my life, and I was wrong. I mean -- I'm such an indecisive person to begin with, so this was far out of character.
It's been a year now.. I'd be lying if I said I still don't think about her each and every day. She keeps popping back in to my life, keeping me at arms length, leading me on and then vanishing. I go on dates, thinking that 'hey, if there's one, there's gotta be more' -- but every girl I meet re-enforces the fact that she was the one. Now, that's not to say my heart hasn't jumped since. I am starting to get some of that capability back. A co-worker of mine has actually caught my attention.
For the first time in a year, I can look at someone, and 'see myself with them'. You see, after her, I wasn't even attracted to the most beautiful girls in the world -- because nobody could be as beautiful as she was. But fortunately, now that is slowly starting to fade.
I'm sure that this sounds pathetic; and to some degree, I'm sure it is. I often envy the people who can just 'ghost' out someone else and immediately severe emotional ties; but unfortunately, that's not me.
You say you give everything until you have nothing left; oh boy, am I guilty of this... but I think that there is merit in learning to be selfish sometimes.
Anyway, you need to take a few things away from this, as I have: