I imagine you cannot think too much about things or too much ahead yes? You have to isolate some parts of your brain and wall the certain thoughts off. Yet you cannot do it completely because you will become too lethargic to care about your safety?

How to dull your instincts just enough to not go mad but not enough to get yourself killed from carelessness that perhaps would arise from separating your psyche from the existential dread completely?

What I mean is that when you are huddled in the trench and things explode around everything screams run and panic but you must separate from that feeling yes while still preserving rational thought and some modicum of self preservation instincts?

Edit: This post isn’t wholly theoretical but part of a mental preparation for increasingly likely war. During which I will most likely volunteer