My kids really seem to keep me in check.... No matter what happens in the office, the kids will still be there to give a sense of reality. They don't care what my role is, just that I am Dad and I still need to be there for bath time and bed time stories. Whilst I still do stuff afterhours once kids asleep, my time with them (and my wife of course.. incase she reads this :) ) ensures that work does not completely consume me, as it used to.
Its definitely tough! I try to leave work at work, though that can be hard when a candidate or client needs to talk after hours or when you move into the negotiation stage which often means you need to be available..
I find it really helps to stay fit and play sport as well.