If you're bothered by a single rejection, the best thing to do may be to go out and be rejected at least 10 more times today. After that, you likely won't feel nearly as bad
In the past I found it much easier to call five girls in a row setting up dates, with some accepting, some not, than to fixate on one for any length of time, build her up in my mind, and then ask her (and only her) out. As soon as a girl seems to fit your criteria (if not before, for practice) ask her out. If she says no, thank her and move on.
Whenever a date would finish, being in a good mood, I'd immediately start the next round of calls, setting up dates with other people (I was seeing 2-3 people per day at the time). For the past year I've happily been with one lovely girl. I feel much more comfortable/confident with her than I would have had I not had much experience before. Many girls in the past have said they like being with me because they feel comfortable doing only what they want, with it being perfectly fine to say no to what they don't.