This is so important. I have a 3yo and wife, I currently work for a series-A startup - It's incredibly easy to do things out of hours, answer messages, train, lab things up, etc... But at the end of the day that is a part of my career.
So except for when I'm traveling for work, I don't do a GD thing past 5pm, unless i choose to. When I choose to, it's likely because a lot of my team is in IST time zone rather than EST.
When you're a family person, your job is to be there for yourself first, your family second, your other commitments after that.
I have a weekly 4:30p friday call. Would i rather have that at 1:30p? Yes. But i've chosen to work remotely in Ohio instead of move to Cali like the last four companies have asked. So I take that friday 4:30p call.
But you better believe that i check out until monday after that.
During the week I'll take odd hour calls for my counter-parts in IST, but that's nearly entirely out of courtesy than necessity.
Take care of things in the following order:
1. You, as a human, holistically
2. Your family, spouse first, kids second
3. Your work
4. Everything else
It's reduced a huge portion of stress from my life by doing this.