I think that this is a tough night for many. This could be just me but it really seems like a celebration of drinking. Another post put it perfectly, it's almost as though "What happens New Years Eve stays with New Years Eve". It's an anything goes night. Listening to people all around you discussing plans, etc etc.
The reality is that I know that no attempt at drinking will ever end well for me. I can't make plans and enjoy myself, it just can't be done. I accept that fact but it doesn't stop me from reminiscing about the excitement of the planning. It's just realizing that the outcome can never be planned for.
I will be one ecstatic person when tomorrow morning comes though.