What you are describing is not uncommon. Many players feel the similarly, especially when playing for real money. There are some things that can be done to reduce both the frequency and the impact of such reactions. Here are a few suggestions, but how effective they are depends much on your circumstances.
- Play more: This is a sensitivity and can thus be desensitized. I do not mean play a wider range of cards (though with the right strategies and circumstances, it accomplishes the same goal). This is more a matter of experience and does dissipate with time. Especially if your response typically goes away when the hand is over.
- Play a lower stake or play SNG or MTT tournaments: The issue may arise from the attachment of chips to money. That is, money directly relates to survivability which can trigger fight or flight. In my case, I mostly resolved the issue with lots of SNGs where money is a prize attached to placement, rather than stack size. After winning a lot of SNGs (and playing a lot of hands), I was able to move back over to cash/ring games.
- Play online: Sometimes this response can exacerbate other anxieties or conditions and vice versa. Removing faces and persons from the equation can help to mitigate comorbid conditions.
- Take Notes/Study: The brain freeze during fight/flight is not unusual. While adrenaline increases the amount of stimuli (information) one can take in, cortisol inhibits brain activity and recording. The only way to offset this is with knowledge practiced and repeated. In fact, the more equipped one is with practice and knowledge, the less often the response appears as the brain perceives these less as a threat.
- If you only primarily get it in heads-up hands, consider playing heads-up games.
It is important to note that fight/flight is incredibly useful, when properly aligned. While it can be annoying, it is also a valuable indicator that there is something amiss and one must be wary. It's not always right, but should never be completely ignored.
In my personal case, I did all of the above and significantly reduced the response and the lack of action (or poor action) caused by it. Now, whenever it appears, I don't get the freeze part anymore. I still get it under the following (known) conditions:
- I 3 or 4-bet a preflop and there are lots of callers. Thankfully, it slows me down so I may attempt to identify the correct play.
- I go heads-up in a large pot against a complete unknown (cash games only).
- I bluff heavy and the villain still hasn't decided whether to fold or call.