Pilots need to have great self-awareness; they need to understand what they’re capable of. Each flight is different, so while pilots do a thorough check of their aircraft, they must also evaluate their fitness for the flight. They must create a checklist to help them understand if whether or not they are prepared for that specific flight. They have checklists for everything and for this particular assessment they have the I’M SAFE checklist to fully understand their capabilities for flight.

I’M SAFE checklist

Illness – Do I have any symptoms?

Medication – Have I been taking prescription or over-the-counter drugs?

Stress — Am I psychological pressure from the job? Worried about financial matters, health problems, or family discord?

Alcohol — Have I been drinking within 8 hours? Within 24 hours?

Fatigue – Am I tired and not adequately rested?

Eating – Am I adequately nourished?

Emotion – Have I experienced any emotionally upsetting event?

Being a pilot is not the easiest job, you don’t get to just not feel like working or think that you might fall ill, still go to work and hope it’ll pass. Quite the opposite, you need to make sure that you are well, ask yourself these important questions and be physically and mentally ready to do your job because people’s lives depend on it.

Source: Guided Flight Discovery: Private Pilot book