Thomas Szasz, somewhere or other, said that it was important to learn to say "no" about small things, that otherwise you might end up holding onto all your small noes and saying one big NO that will actually prove calamitous.
In my youth, I was very impressed by Szasz's critique of the "mental illness model". I still think there is a lot of overrated science involved in the whole DSM approach to the categorization and diagnosis of mental disturbances.
I thought this was interesting from the Wikipedia article on Szasz:
Szasz argues that only mental illnesses are defined based on consensus and symptom clusters. It has been argued this is not the case. Critics claim physical illnesses such as Kawasaki syndrome (a disorder of the heart and blood vessels) and Ménière's disease (a disorder of the inner ear) are similarly defined.We know so much more
than we did before,
but the detailed workings of the brain,
whether sensible or delirious,