2. Sort out your desk: chair, keyboard, screen, the works. Do the maths: compare the cost of a decent back-friendly chair with the cost of repeated visits to the back-injury clinic, MD, physio, or chiropractor. DUH!
3. Forget about "just checking my email for 5 minutes": it's the well-known "gambler's fallacy" ("just one more bet and my luck is bound to improve"). Do the maths: what's the true average length of your so-called "5-minute" sessions? Time it! And set a quitting or a pause/break time... DUH!