I.M.S.A.F.E.

IMSAFE, in flight instruction and piloting, stands for a group of six variables that the FAA (US) considers measures of good fitness to fly:

I - Illness
M - Medication
S - Stress
A - Alcohol
F - Fatigue
E - Eating

Knowledge Management Space

FAA checklist: The six listed items with some further information.
Wikipedia: This Wikipedia entry for IMSAFE simply repeats what the previous one says. However, it calls the attention to a common confusion, whereas E is defined as "Emotion" rather than as "Eating".
Tom HAMILTON's (1999) Checklist: It provides further explanation on each of above items. Although written for balloonists, the message equally applies to pilots.