Cynics doubt everything so they never have to think. Critical thinkers doubt so they can think better.

Blanket doubt is a labour-saving device dressed up as intelligence. If everything is corrupt and everyone has an angle, there is nothing left to examine, which ends the work before it begins. Real doubt is narrower and more expensive: it targets a specific claim, says what would settle the matter, and is willing to arrive somewhere.

Watch for the moment your doubt becomes total, since that is usually where it stopped being useful. Ask what it would take to convince you, and find out whether that exists. Doubt that starts an investigation is worth keeping; doubt that ends conversations is just fatigue.