Honestly, I'd wager you're quite the anomaly. Most people with a poor work-life balance are going to have their overall happiness take a hit. Sometimes severely, and especially with the schedule you are describing unless their other obligations in life are few and far between.
It's not just about expectations, but other important things in your life that keep you happy. If you're married to your job and that's the most important thing to you - sure, you'll be happy. But if you have significant others, family, hobbies, other things that give you joy....working 6-7 days a week and leaving at 8pm every day for year after year is going to seriously wear the average person down. I can't imagine having that schedule and not completely breaking down, and I consider myself a pretty hard worker.
I guess what I'm saying is, giving advice like this without a huge caveat isn't a good idea because it's not applicable to the vast majority of people. Kinda like saying "Oh, the debt isn't that bad because I live in a hovel, eat ramen, and put every penny towards it" when most people have other expenses or want to live a halfway decent life.
