Human performance limitations
The pilot is part of the system
However automated the aircraft, the human decides. IMSAFE is the standard self-check: Illness, Medication, Stress, Alcohol, Fatigue, Emotion/Eating. Fatigue degrades attention and decision quality long before you notice it; stress follows an inverted-U curve, helping at low levels and destroying judgement when high. Complacency is the quiet killer in drone operations because the aircraft appears to fly itself.
Perception, attention and decision-making
You are watching a two-dimensional screen through a narrow lens. Camera field of view is far narrower than the human eye, depth cues are lost, and height and distance are hard to judge - which is exactly why VLOS is a legal requirement and why an observer helps. Inattentional blindness means you can stare at the screen and miss an aircraft approaching from the side. Watch for hazardous attitudes - anti-authority, impulsivity, invulnerability, machismo and resignation - and for plan-continuation bias: the pressure to complete a flight because you have travelled, paid or promised.
Trap: 'the aircraft flies itself, so my workload is low.' Monitoring is a high-workload, low-stimulation task; boredom is a bigger threat than overload on a routine flight.
Rule of thumb - three strikes: if three things are already going against you (late start, wind above forecast, low battery, a crowd arriving, a nagging doubt), stop. The flight will still be there tomorrow; the doubt is data, not weakness.