I'd have done the same thing. Because I am a social idiot too (I mean that in the nicest way). And honestly, I bet they probably felt the same way as you, just they had more experience in the social skills department. They were all 'prepared' not 'connected'.

Don't beat yourself up... I know its embarrassing, but take it in stride and think about it for next time. Not that you will feel any different when you hand your cards and candy over, haha.... personally I would have been grinding my teeth at the ridiculous ceremony granted to underline its specialness (it already was without the cards, right? I mean at least the graduating part).

edit - and btw CG on completing your therapies!!! (I can't even make myself go... but I can tell you what, thanks to you I will be ready with my cards and platitudes at the end!) :P