A person can leave the battlefield and still wake up every morning prepared for war.

Vigilance built under real threat does not switch off when the situation changes. The scanning, the light sleep, the readiness for something to go wrong: these were accurate responses to the environment that produced them, and they persist into rooms where nothing is coming. Your body is still running a correct program for a place you no longer live in.

Be gentle about this rather than impatient. Notice when you are braced and nothing is happening, and let that be information rather than a fault. If it has been going on a long time and is exhausting you, it is a reasonable thing to get help with, and help is available.