Unfamiliar terror-tory

I have a date tomorrow night. To say it's been a long time since I went on a date (or even a pseudo-date) would be an understatement. Even just in the realm of male attention we're talking nigh on four years. That's a little embarrassing to admit. Ok, a lot embarrassing. Were that the end of it, I probably wouldn't be overcome with such a immense feeling of trepidation and desire to run in the exact opposite direction.
But it's not.
After spending eight months of last year recovering from a knee injury, unable to exercise much and living with my mother's need to constantly feed me, I've put on quite a substantial amount of weight. Coupled with countless hundreds of job rejections - yes, that's how unemployable I apparantly am - I'm feeling very much unlike a person anyone could ever get to like, let alone find attractive.
Nothing fits, nothing looks good, and nothing makes me want to cry more than trying to find an outfit to make me seem attractive in the eyes of the opposite sex. And I hate myself for being so damn reliant on the opinion of a complete stranger to make me feel ok about myself. But I'm so damn scared of that rejection I honestly feel like throwing up every time I think of 7pm tomorrow night.
So I'm begging for some advice. What do you do to pep yourself up when you're not feeling grand? How do you overcome the nerves before a date/interview/big-deal event? What's your sure-fire trick for impressing the pants off someone?