With difficulty! :frustrating: I totally empathise - it's just so difficult when we (a) see the best in people and paper over or choose not to dwell on their flaws (b) have such a great imagination, that half the time the person we are in love with barely exists in reality. I speak from experience, not judgment, I hasten to add. I have been in love 3 times.
The first one, I began to let go of when I stopped seeing him around (he left work) and also realised he didn't have the same ideals of friendship i.e. wasn't there for me when I just wanted to talk as mates. What really did it tho was channeling my emotion into passing my final accountancy exams, tricking mysekf into believing that one day I'd meet him in the street and be able to show that I was intellectually "good enough" for him. By the time I'd passed tho, I had ceased to believe he was the one.
The second one, I began to let go when I finally realised I had imagined who he was - he started talking about ironing (rather then anything philosophical) and I realsed I really don't want to be spending the rest of my life with somewhere so concrete!
The third, well this one was recent; I still believe he was different and the right one and he may well be still, but it was wrong timing. If its meant to be, it'll happen is what I comfort myself with...and channelling my emotions into climbing - I guess its like the first one, he's a climber so I feel like if/when we meet again, I at least want to be better than him and show him I was a good enough climber for him.
Kinda stupid logic I know, but the moping and pining is really not helpful - starting a new project with an important goal/achievment at the end, and making the motivation for achieving it the other person, well, that's what's helped me in the past...and even if the person doesn't come back, you manage to let go and also achieve something to be proud of in the meantime.
Hope that helps a little!