There Are No Desperate Situations, Only Desperate People.
I am always mentally prepared to go the full length of the contractual duty time for each flight, which is a fixed number of hours, depending on whether it's a domestic or international sector.
If all the delays can be accommodated without exceeding that duty time, then the flight can begin, otherwise it would be time to go to the hotel.
It's hardly a stressful decision. Either one can or can't complete a flight within the regulated duty periods.
To be sure, I'm always planning and expecting a missed approach at every destination, and a diversion to the alternate airport, so as to preclude at least one "surprise" event.
As to whatever else may happen: I don't worry in advance!