>>1
tl;dr. ...Crap, I did read. Oh well.

short version: stop. get over her. get a life.

long version: You think she's that special because of how she's affected you, because of how much she has affected you. But the truth is, she isn't that special (as a potential partner), and you're only hurting yourself. Normally, a really bad way of going about things would be to actually try to get over her, i.e. trying to focus even more on her, just in a different way. You need to start trying to keep your mind busy and interested in other things, not to forget her, but to make your life less focused on her, and more on other things. Keep doing things that makes your life feel full and rich. There's nothing wrong with feeling grateful for all that she has done (provided extra incentive for you to become even better at Japanese, etc), but try to see that it is the limit, that was her purpose in your life. Feel grateful over the past, embrace the rest of your life.