You were a pussy. You stalled because you lacked the balls to make a move. You missed your shot. Sorry. You've done it before, you'll do it again.
I'm going to be very blunt because you need to hear this and you do seem genuinely nice (to a degree) and I hope your luck will change: You sound like a weak, whiny fucking bitch, and that's probably why you live a life of repeated cockblocks.
When a normal guy seeks a hot girl he thinks, "FUCKING EH, I'M GONNA GO ASK HER OUT!" And then he pounds four of five beers, staggers over and gives it a go. Shut down? Fuck it, do it again thirty minutes later with a different girl. You see a girl you like and your immediate thoughts are: OH NO, AM I TOO FAT? AM I TOO UGLY? AM I TOO BALD? AM I TOO POOR? MAYBE I'M A CLOSET FAG AND JUST LIKE HER SHOES? Then you wring your hands for an hour, all the while droning on to anyone nearby about your feelings, and your fears and your insecurities, and when you look up one of the normal guys has already bought her a second round of chu-hais and practically has her panties down.
There is a defined group of males who make educated arguments that females are drawn toward men who are sensitive, and in-touch with their emotions and inner-beauty, and who love to express their feelings; these men are called PUSSIES, and are usually virgins who will die lonely (or married to a grotesque thing 30lbs heavier and 40 years older than them). You need to knock that shit off NOW.
I don't give a shit what your friends from the high school chess club told you. Women don't want a whining, insecure pussy who bleats on about his feelings and cries like a fucking adolescent girl. What can you do? Marlon Brando put it well: "YOU CAN ACT LIKE A MAN."
First, you say that when you're attracted to a female, you worry you aren't good enough. This is easy. YOU PROBABLY AREN'T. So lower your expectations.
Next, ACT LIKE A MAN. Go to a large party, gathering or gaijin bar. See any girls you think are attractive? Found one? Nope, you're probably too fucking ugly. Lower expectations, remember? So now try to pick out one you think inhabits roughly the same level of unattractiveness that you do. Preferably a lonely looking one with prettier friends. Found her? Good, now pound a few drinks and walk over and start talking. You do NOT talk about yourself, do NOT talk about your feelings, do NOT whine about anything. For once in your life, ask her about HER and stick with that conversation as long as possible because you already know you have a habit of focusing on yourself.
If you can manage to successfully man-the-fuck-up and get her into bed, then congrats...you've now established a baseline. You can score with a girl "that" ugly. Now, you work your way up. Keep trying it out with a girl just slightly prettier, until you've hit a level of attractiveness where you keep getting shut down. Then you know your limits.
I've just solved your life for you. Next, I run for President.