And after you finish all of that you absolutely want to spend those last few hours sitting down and resting. You will quickly burn out if you spend every minute busy.
Unless the work is a rest time. Not every job is demanding and if one turns of emotional reactions to workday situations then one will have more energy for later activities.
That's funny, it almost sounds like you're suggesting it's common to have a job that's more relaxing and restful than actual leisure time.