It’s a reflex.
It’s so easy that it is almost impossible to stop yourself from snapping at loved ones when you are stressed, cranky, tired, hangry or pushed to the limit by whatever. It’s proximity, just like the nerve reflexes your doctor checks with the little rubber hammer thingy. Particular nerve reflexes are wired so that they basically short out across the spinal cord and bypass the brain entirely. Your leg moves with the hammer boink without you thinking about it or willing it to do it…or not do it. It’s the same brain-bypass that lets you snap your hand back from a hot pan so you don’t get burned.
Reflexes bypass language editing centers. I don’t know about you, but when one of those injury avoiding ‘ouch’ reflexes happen, it is usually accompanied by at least “OW” and usually a swear or two. Reflexes happen faster than cognitive processing, they don’t go all the way to the brain and have a shorter distance for the nerve impulse to travel, for a simplified way to look at it.
The same is true when we are under stress. It is quick and easy to take it out on loved ones because, with any kind of luck, they are relatively close at hand. The stress has a short distance to travel. If you are the stressed one, it is hard to stop yourself from doing that. If you are the one in the splash zone of your loved one’s stress, it is hard to stop yourself from getting reflexively defensive and splashing a little bit too.
I’ve learned this from my spouse who is a freaking saint to put up with me my crankies, but taking care of yourself is an act of love for the ones you are closest to. Get a nap, have a snack, whatever it is that works to manage your stress…DO it. You’ll be doing a favor for your own mental health as well as giving a token of affection to those who you love…and who love you.