Try to get a good nights rest, get some exercise when you get a chance, and do things that you enjoy and make you happy and it will translate into a positive mindset for when you play cards. If you are battling boredom try listening to music or watching a show/movie. If you are not in a good mindset it's important to take a step away from the tables (even for a little bit) and come back when you are refreshed.
Its called mindfulness hehehe the act of training your brain to keep concentration.. Corps are using It now. I'm trying to practice as Wellington.a very good way to disconnect in the world and get into the game's vibe, it's the DeRose method, it's the Hipionese base, and commands that you send to the brain, one that I use is kept listening to the pulse clock, listen to the clatter of the pointer, I fix my attention on his clatter and put a song to play in a high tone, and I am increasing and I concentrate to continue listening to the roar of the clock, the pointer to beat every second! it makes me focus and stay focused! for me it works! anyone who has research interests on this!