When someone is operating while fatigued, even when that someone is an adult, his or her experience changes dramatically. Moods become low. Demoralization can set in. Negative thoughts seem more realistic. Requests from others seem more intrusive.
Small worries can become major anxieties.
Kind suggestions can feel like hostile criticism. What seemed like a simple task just hours ago appears now to be a burden or an imposition. During times of fatigue everyone is less of themselves. People are moodier, snappier, they may be more prone to tears or tirades, they are often more easily hurt and less hesitant to hurt others. When tired, people are less in control of both thoughts and emotions and when fatigue states become extreme moods can look labile or highly fluctuating and out of control.