What else helps you to stay cool, calm and collected while you are playing?
Reading "The Mental Game Of Poker" by Jared Tendler helped my game sooo much! I see you mentioned you read it so you might be familiar with a method he calls "Injecting logic"... When you endure a bad beat, take a breath and tell yourself that you made the right decision and it was a winning play in the long run. This will help clear your current frustration before it builds up and gets worse if you get drawn out on again. I know it sounds simple. But it's helped me clear my mind and stay focused. I don't let all the bad beats build up my anger.
“Injecting logic works best when: You catch the build-up of emotion, such as tilt or fear, before reaching your emotional threshold. If not, you have a major uphill battle to regain the ability to think clearly and play well without having to take a break or quit. Why? Once your emotions have crossed the threshold, it becomes harder and harder to think clearly. Injecting logic is really just thinking. Therefore, if your emotions have shut off your ability to think, trying to inject logic is the equivalent of trying to run on a sprained or broken ankle. Your logic also corrects the underlying flaw. The fastest way to resolve a mental game problem is by injecting logic that also corrects the underlying flaw that is causing it. Basically, you’re working toward two goals at once.”
Success is dependent on how you manage the variance. Keep injecting that logic and treat every single hand independently! Even when you're on an upswing, don't call your gutshots against the odds or call when you're blatantly beat on the flop trying to hit your 2 outer on the turn because you're "hitting everything" lately.
I tell these things to myself over and over and it's drilled into my game now