Running maps all day is dull. Not everybody can be like Ziziran and perform PoE goods for 16 hours per day daily. It didn't help that my friends had died and quit the league.
If you are serious about winning a race in Path of Exile, you want to get in the mindset of playing just "an additional map" And after you complete it, run one more map. Set up a movie or a music playlist which gets you to the groove, and just keep going. Make it second nature to start another map as soon as you exit, so that you have to keep grinding.
That being said, it is important to keep healthy and sane, and 16+ hour days aren't healthy.
You make better decisions when you are well-rested. If you do not get enough sleep while you're competing in a Path of Exile race, you will make a sloppy error and die.
Throughout long grinding sessions, be sure to step away from the computer every few hours. Spend 30 minutes doing something that doesn't involve looking at a screen.
It's not that the end of the world if you die or do not get a Demi. I died twice at the Turmoil race. The second time was very unsatisfactory because I was at the top five to my class at the moment, also this was the very first race I had ever tried to triumph. Both of those times I expired involved elderly mechanisms, but I learned from my errors.
Back in Mayhem, I made a stupid decision on day six and died, but made yet another character instantly and kept pushing. I was in 2nd spot for my course when this happened.
Was it tough to start over? Sure. It would have been easy to just mope around to buy chaos orb. But I decided to be proactive and keep pushing, and I was lucky enough to finish fifth in the class I'd died on, and made top five for the new course.