That’s very normal, especially when you’re new. Long sessions can be mentally exhausting. The key is to focus on session management, not just endurance.
Try playing shorter, high-quality sessions instead of very long ones, take regular breaks, and stop when you feel your focus dropping. Having a routine helps a lot — good sleep, hydration, and light exercise make a big difference in mental stamina.
Over time, as decisions become more automatic through study and experience, the mental energy required decreases. Longevity in poker is more about consistency and discipline than grinding endless hours.