So sounds like you are one of the lucky folks who is excited and really enjoying their day job that you dont need a challenge after work. I once heard that those who are very stimulated at work actually spend a lot of energy and need cool down "after work". I (like many I know) can't wait to get home after a soul crushing day (at a pretty well paying job) to work on exciting things! Depends on factors that energize and motivate you I guess!
There are also people who hate their day job, and after dealing with food, chores, and physical fitness, just want to spend their last waking hour or two relaxing before starting over.
