What you divulge about yourself on the first date will undoubtedly determine whether you score...another date. Sure, we want men to be vulnerable. We just don't want them to share their every well-guarded secrets (or tic, quirk and fetish) on the first date. That comes across as damaged and weird, and it takes the fun out of the whole getting-to-know-you song and dance.
Trust, if you give it all away on the first date, there is no chance she'll follow suit (if you know what we mean). Your conversation should be fun and light. You should be charming and tell upbeat, intriguing stories. You should not be talking about the disturbing childhood memory you have that scarred you for life. Women have sex with the idea of a man, an idealized image he projects, and no one wants to get down with the guy who gets dewy-eyed talking about how Fido died when he was 8-years-old or waxing emotional about how his ex-gf used to order her steak medium rare, too. You build up to sharing these things, guys! Or in the case of the latter, you don't.