Burnout is the result of ongoing frustrations, difficulties, social masking and fatigue, and when there's little or no chance of rest and recovery time after a stressful experience before the next one comes along.
When someone's in 'burnout', the smallest tasks can feel overwhelming and there's no motivation to do anything.
The person in burnout tries to keep going and it actually takes up more energy than usual for them to do this and this extra effort, or drive, can turn into extreme tiredness and fatigue.
Autistic Burnout is usually a consequence of camouflaging or masking for either an extended period or over a period of time without a break, as it takes a huge amount of effort. It can also be a result of sensory overload, executive functioning demands (juggling too many tasks at once), or stress associated with unexpected change(s).
Over time, burnout can affect a person's overall health as the body's resources are being used, and not being replaced, which also leaves nothing spare for any recovery.
Whatever the reason for Autistic burnout, it has very real and significant impacts on an Autistic person's overall functioning and happiness as they're in a constant state of high alert and anxiety and might also feel inadequate, knowing they don't fit in.