I agree. Keeping the mind busy & focused is the key.
Before I go camping I like to think thru the RULE of THREES because it gives me a structure & helps me to relax & then I know I haven't forgotten anything that matters. Then when I get there I go thru them again. If ever in a true survival situation that is what I will be doing as well.
The best thing to keep you from worrrying & freaking out is to stay focused on the priorities - don't concentrate on what you don't have.
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Take the analogy of dieting. If you sit there & think about not wanting a candy bar in the machine down the hall you will eventually cave in & go get one. In a survival situation if you sit there thinking about the bugs & the dark you will go crazy.
Instead if you find other things to concentrate on - the healthy food you going to enjoy later, your work or whatever keeps your mind off what you don't want to eat then you have a better chance of success.
In the same way if you focus on making a fire (which itself will take care of the bugs & the dark) you will be successful. Even if you are not able to make a fire then get yourself as comfortable as possible & close your eyes & focus on the next day when the sun will come out.
It's a mental game where we must go on the offensive.