I'm going to mention one you may not have on your list of borrowed things to say, but is worth considering: If you're in a situation where any sort of confidence at all is probably hubris, I recommend Purple Tentacle's opening shpiel from Day of The Tentacle: Nonsense. I feel great! Smarter! More agressive! I feel like I could... like I could... TAKE ON THE WORLD!

Depending on where you socialize and the nature of the attitudes towards social lubrication of the people you socialize with, the Green Tentacle's line which precede that ("Dude, I don't think you shoud drink that...") may also be appropriate.