In other words you should always be willing(and able) to cancel a flight under any circumstances or areas of caution.
Checklists are key, but the pilot must be willing & able to take appropriate action when a checklist item fails or cannot be completed -- i.e., stand down & cancel, instead of "it should be fine...".
That failure to cancel is two of the three items usually needed for a crash (the failure itself and the bad pilot decision).
Ok, going 40mi you have only so much weather than can go wrong, but I've had friends trapped at an airport due to weather, leave their plane and drive/fly commercial home. It's a fun hobby though. :D