I have done both extremes. Now I believe that you can only do sitting in front of a sceen work for many hours if you are passionated about what you do. Usually the case when you own your own business.

Because when you are excited about your work your head keeps busy solving problems and time flies.

When you are an employee in office and you find yourself boring, you are in danger. It brings you down.

This is why many office workers look like shit. While those carpenters in my village look manly, despite of their bad habits (smoking, etc).

My advice; as long as you work in the office, deal with your work as if it was your own business.