A notification is someone else deciding what you think about next.

Every alert is an interruption whose timing somebody else chose. Your attention goes where it is pulled, so what occupies your mind for the next ten minutes gets decided by an app rather than by you, over and over through the day. That is not a character flaw. It is a system working exactly as it was built to.

Turn off notifications for everything that is not a person contacting you directly. Keep calls and messages, drop the rest. Check the apps when you decide to, which is the entire difference.