Take Scheduled Breaks!
As much as I love poker, I schedule breaks that help me stay fresh long term and keep the game from becoming stagnant. Every week I try to take at least 1-2 days off from playing and every few months I take 4-5 days off straight from playing to focus on other hobbies or a vacation. It's important to balance off the table as well, so if you feel at any point that you don't actually want to play or are feeling mentally drained from playing a lot of hands/hours recently, then take a break and go find something else fun to do!