Illness - Is the pilot suffering from any illness or symptom of an illness which might affect them in flight?
Medication - Is the pilot currently taking any drugs (prescription or over-the-counter)?
Stress - Is the pilot overly worried about other factors in their life? The psychological pressures of everyday living can be a powerful distraction and consequently affect a pilot's performance.
Alcohol - Although legal limits vary by jurisdiction), the pilot should consider their alcohol consumption within the last 8 to 24 hours.
Fatigue - Has the pilot had sufficient sleep and adequate nutrition?
Emotion - Has the pilot fully recovered from any extremely upsetting events such as the loss of a family member?