Well as the first post talked about rituals, I will share what I usually do, not only for poker, but for my life in general, especially when I wake up.
A few months ago I had contact with a breathing method made by a guy named Win Hof, known as the "ice man",
It is a breathing technique, mixed with physical exercises and exposure to cold. It helps to better oxygenate your body, all your cells, to increase concentration (similar to the feeling of meditation), helping to improve lung capacity (holding your breath is part of the breathing routine), slightly changes the blood pH, making it more alkaline, this improves your energy capacity, and the exposure to cold contributes to your autoimmune system, resistance to pain and fatigue. In short, a very extraordinary thing, isn't it?
So if you find it interesting, get to know the Win Hof method for yourself, and draw your own conclusions.