The notification’s sound is the same whether the message matters or merely exists.

One tone is being asked to represent everything. A delivery update, a friend in trouble, a shop having a sale and a family emergency all arrive with identical urgency, so your body reacts to each one the same way and only afterwards finds out which it was. Attention gets spent before any judgement is possible.

Spend fifteen minutes sorting your alerts so that only a few things can make a sound. Let everything else wait to be looked at. The point is not fewer messages, it is restoring the difference between something that matters and something that merely arrived.