Hi Nina,
It's been a year for me since I've gone back, and I would say it took me about 2 solid months to adjust to a different type of routine, but I think it's all about self-discipline. I would never leave work on time, was always very much dedicated to finishing all tasks.
Now I just plan my work day a bit differently since I never got less hours and cannot work from home. I think it's possible to have a balanced work day and enjoy your home and family if you are well organized and set your daily objectives for the next day prior to leaving work in the evening. This way - at least for me - the sanity is there, and there are no issues with being over stressed. I can also push back newly assigned tasks since I can always speak to what I'm currently working on.
I would actually say that being a working mom made me much more responsible and organized at both work and home. It makes you feel good too - the fact that you are juggling more responsibilities than before.
Hope that helps!