I was a huge second-guesser for most of my hunting career. Granted, I'm 6'4" and so that makes me huge-- been there with the suspended-in-air thing.
But seriously. Second-guessing is when you beat yourself up a forehand, because you cannot make a decision and then beat yourself up afterwards for making the wrong one. My buddy, the ex-Marine, put it succinctly: "The most essential part of leadership is not the ability to make decisions, but rather the ability to make decisions at all. You can recover from a bad decision, but indecision in a crisis will get you and everyone who relies on you dead." That stuck with me.
You usually have to make tough decisions hunting that will determine the outcome of the hunt of even the whole season. Hunting is a series of those sorts of decisions. The trick is to have good sound principles leading you, and then move ahead with the best rational choice-- that isn't much of a trick, is it? Well, that is all there is to it. The hard part is not the theory, it is in the execution.
Secondly, is the beating-up process itself. The trick is to accept that a) that the decision was sound based on principles and the intelligence at hand, and b) that worrying about the past is useless. Save the second guessing for a post-hunt evaluation. Save the hunt for hunting-- stay in the present. If you catch yourself living in the past, ask yourself: Do you want to hunt or reminisce? I can't count the number of times I've blown a shot or some such foul-up and been sitting there grousing about it only to have another nice shooting opportunity arise. Sometimes I have been successful in getting the remonstrations put aside and moving on. Other times, a snort or a white flag coursing through the woods tells me I've been living inside my head, and it is time to get back to reality. My then-best buck in 1992 happened just that way. I was just getting settled into my climbing stand when a nice buck walked by and I was still fussing with my kit and hadn't knocked an arrow. I had to stuff the self-recrimination in a hurry, because 15 minutes later the biggest buck of my life walked up and stood 15 yards away. It comes at you fast sometimes.
Next is the post-hunt evaluation. Turn each after-hunt into a constructive assessment. Don't beat yourself up, but DO (!!!) evaluate all that you've done right and done wrong. If there was a failure, study it. It will teach you more about what you need to be doing next time that a hundred successful days afield. Two seasons ago I had a monster come in on the opener of KY ML season. I wasn't fully prepared, the angle was wrong, and he never fully gave me a decent shot. I beat myself up for a bit, and then finally realized I'd probably done the right thing by keeping the barrel down and just watching fellow in my binos. If I'd chanced the shot, I would have probably mucked it up rushing it.
I've worked as a QA manager. I've worked in manufacturing. I despise this lets-not-find-fault way of looking at screwing up. Too often folks try to hide behind "Let's just see how we can make it better." I suggest a different way: Everyone involved try and figure out how they were at fault and contributed to the problem. But then come back to it clearly and rationally. Most folks hate blame. I love it. What I try to avoid is the emotional baggage associated with it. As a hunter, I recommend that if you screw up, you take a hard look at what went wrong. Was it improper stand selection? Too much movement on stand? Not enough practice at the proper range? Good! Get to the root cause of the failure. Next, see what it takes to correct it and make a plan. Work the plan. Go back out and test the situation measure and review the results. Where this second-guessing emotional meat grinder comes into play is when you a) duck the rational and b) try to live in the emotional side of what went wrong.
Take your recent problems: Gut? I generally do not listen to gut. Gut tells you what to do, but gut doesn't tell you why. If your intuition tells you to do something, you need to take a rational look at what it is telling you. If you go against that intuition, do it for a rational reason that can be compared rationally later. If you don't listen to gut, and you fail? Figure out what gut was telling you so it isn't a big mystery next time.
Take the knee. Look, I've injured myself pretty extensively in the field. I had to come back from a solo backpacking trip on one leg one time. I've had tree stands fail. I've had to drive myself to the emergency room. Stuff like that is going to happen. In all cases, there was a reason why I went out and a reason why I took the risks I did. Nowadays I refuse to go afield ill-prepared, because I'm in my mid-fifties and small things can turn big. However, if I screw-up ( and I have) and I end up paying for it, there was sound reason why I went out, and an unforeseen consequence that needs to be planned for the next time around.