Fatigue is different from drowsiness, where a patient feels that sleep is required.Temporary fatigue is likely to be a minor illness like the common cold as one part of the sickness behavior response that happens when the immune system fights an infection. Prolonged
Prolonged fatigue is a self-reported, persistent (constant) fatigue lasting at least one month. Chronic
Chronic fatigue is a self-reported fatigue lasting at least six consecutive months. Chronic fatigue may be either persistent or relapsing. Chronic fatigue is a symptom of many diseases and conditions. Some major categories of conditions that feature fatigue include:

Autoimmune diseases, such as celiac disease, lupus, multiple sclerosis, myasthenia gravis, Sjögrens syndrome, and spondyloarthropathy
Anxiety disorders such as generalized anxiety disorder
Blood disorders such as anemia and hemochromatosis
Cancer, in which case it is called cancer fatigue
Chronic fatigue syndrome (CFS)
Substance use disorders including alcohol use disorder
Depression and other mental disorders that feature depressed mood
Developmental disorders such as autism spectrum disorder
Eating disorders, which can produce fatigue due to inadequate nutrition
Endocrine diseases or metabolic disorders: diabetes mellitus, hypothyroidism and Addison’s disease
Fibromyalgia
Gulf War syndrome
Heart failure
HIV
Idiopathic chronic fatigue (ICF), which is chronic fatigue with no known cause that does not meet chronic fatigue syndrome criteria
Inborn errors of metabolism such as fructose malabsorption. Infectious diseases such as infectious mononucleosis or tuberculosis
Irritable bowel syndrome
Kidney diseases e.g. acute renal failure, chronic renal failure
Leukemia or lymphoma
Liver failure or liver diseases e.g. Hepatitis
Lyme disease
Neurological disorders such as narcolepsy, Parkinsons disease, Postural Orthostatic Tachycardia Syndrome and post-concussion syndrome
Physical trauma and other pain-causing conditions, such as arthritis
Sleep deprivation or sleep disorders, e.g.
Without GABA absorption to those particular nerve rootlets (usually centred, in this case, around the sectors L1-S1 and L2-S2), affected nerves (here, the ones controlling the legs) perpetually fire the message for their corresponding muscles to permanently, rigidly contract, and the muscles become permanently hypertonic (spastic).The abnormally high muscle tone that results creates lifelong difficulty with all voluntary and passive movement in the legs, and in general creates stress over time—depending on the severity of the condition in the individual, the constant spasticity ultimately produces pain, muscle/joint breakdown including tendinitis and arthritis, premature physical exhaustion (i.e., becoming physically exhausted even when you internally know that you have more energy than you are able to use), contractures, spasms, and progressively worse deformities/mis-alignments of bone structure around areas of the tightened musculature as the persons years progress. Severe arthritis, tendinitis, and similar breakdown can start as early as the spastic diplegic persons mid-20s (as a comparison, typical people with normal muscle tone are not at risk of arthritis, tendinitis, and similar breakdown until well into their 50s or 60s, if even then).No type of CP is officially a progressive condition, and indeed spastic diplegia does not clinically "get worse" given the nerves, damaged permanently at birth, neither recover nor degrade. This aspect is clinically significant because other neuromuscular conditions with similar surface characteristics in their presentations, like most forms of multiple sclerosis, indeed do degrade the body over time and do involve actual progressive worsening of the condition, including the spasticity often seen in MS.