Having kids is the ultimate sacrifice - you kiss your old life goodbye, and probably will never see it again. Now, you do this for good reason and it's totally worth it, but it takes a minute to adjust and realize life is never going to be the same again.
Take working out. I am a big fan, always have been. I get in a bad mood if I don't work out every day. Used to do an hour, even an hour and a half sometimes - and now I am LUCKY to get 45 minutes in. And that usually entails a few 15 minute blocks interrupted by the baby spitting up or having to turn on Peppa Pig while on the elliptical instead of getting all caught up on my Bravo shows. (I know, enter tiny violin here)
Another thing that has changed: my Saturdays. I don't even know what I used to do before kids, but it probably involved watching basketball and day drinking. And now it looks like multiple child birthday parties, and probably next year adding a soccer game into the mix. So basically day drinking might still be a necessary part of the day.