Alertness

Alertness is the state of paying close and continuous attention. It is the opposite of inattention, which is failure to pay close attention to details or making careless mistakes when doing work or other activities, trouble keeping attention focused during tasks, appearing not to listen when spoken to, failure to follow instructions or finish tasks, avoiding tasks that require a high amount of mental effort and organization, such as projects, frequently losing items required to facilitate tasks or activities, such as supplies, excessive distractibility, forgetfulness, procrastination i.e. inability to begin an activity, difficulties with activities (cleaning, administrative, etc.), difficulty falling asleep which may be due to too many thoughts at night, frequent emotional outbursts, easily frustrated, and easily distracted.

Diseases
Alertness is related to psychology as well as physiology. People who lack alertness may have narcolepsy, attention deficit disorder, chronic fatigue syndrome, depression, Addison's disease, or sleep deprivation.