Here's a secret: Everybody always tells you how much they work, nobody ever tells you that they take time off. It's like a cult in consulting. Especially managers/principals/partners who have a much more flexibility and freedom do not always work - they just don't tell anyone about it.
True, when you start out, you do not have that luxury. However, there are certain projects which are less demanding, there is time in between projects, there is vacation and you can take sabbaticals. Finally, you can let your project leader/manager know about things which are important to you. I had team members who wanted to hit the gym and do a bit of work afterwards, or had specific times which were important to them. One team member had a family, so he wanted to be home a bit early each Thursday to see the kids, which we made possible every week.
But kid you not, in the end consulting is demanding. But you also learn a lot, and you don't have to do it forever. For me it was funny, I thought I did a lot in high school - until I went to university where I felt I had to do much more. Then I went into consulting, and only there I learned how much you really can get done in a week in a small team with smart individuals. :)
All the best!