HELP!!

This is my first pregnancy and I'm 26. Yesterday I found I'm having a baby girl. I've wanted a baby for so long so this is my dream come true, but what I can't work out is why am I so sad about missing out on drinking or just having a pint at the pub with my friends. Before I got pregnant I thought I'd be ok with not drinking or partying as I've had a good few years having fun. Anyone else feel like this?