LMAO dude you're such a joke. I just went through the thread where you were praising asceticism, and now you sound like a hound in heat. The hypocrisy is that you act all haughty intellectual and above the superficiality of regular peeps, yet what has you excited is that girl's looks and how you want to nail her. Ever thought why you don't look for rejected ugly girls? I bet you'd find at least a few interested in you and your intellectualism. You're just like everyone else, pal, guilty of the same thing. Get off your high horse and stop looking down on peeps doing and having the same stuff you WISH you could do or have.
I think I know where your depression comes from: lack of honesty with yourself. Your thoughts are contradictory to your own self and way of being. There is an internal conflict between what you preach and who you are. Grow some balls, make an honest evaluation of what your real values are, accept yourself the way you are and start working for betterment in a realistic manner. Holding yourself to high standards and falling short of them makes you bitter and frustrated. You're not as smart, morally perfect or right about stuff as you want to be, as you sometimes delude yourself to be. Getting off that high horse should do wonders to your mental health pal.
Also, did the other guy ask you to back off and you agreed? If not, the girl is fair game. If anything, you should get some balls and inform him as soon as possible you're interested in the girl. A lot of men back down just from that. If he doesn't, then he can't say you didn't give him a fair warning right?