it can take a toll on you if you don't track it correctly. you should look into what causes you to stress. it could be something outside of poker, maybe job, friends, family, physical pain. It could be relationships, or even unhealthy dieting. Lately I been stressing myself, and I think mainly it was due to being lazy, and being to stubborn and not admitting that I needed to fix whatever it was that is making me lose. so i started playing less and just blocked myself from trying. I think I stress over on my results and really just blamed poker when in reality, I wasnt putting in the effort on practicing. I still get frustrated, but its important I start to acknowledge my effort because even though I had won before, I probably wasn't as good as I am now ..each player has a different way of practice and approach, look into mental endurance and setting goals, look forward to learning a new approach other than stress.