I'd suggest always sitting in front of the computer to see what opponents are doing. Don't watch a movie/TV to distract your mind because you should concentrate on your game. Avoid any social media site too.
Too stay fresh drink lots of water, listen to music if you want (preferably music with no vocals such as edm, classical, instrumental etc as it is less distraction), get up and walk a little, do a little bit of yoga while sitting (breathing exercises), but don't distract yourself from the game.