What is the only effective way to counteract driver fatigue, according to the AAMVA CDL Manual?

AAMVA CDL Manual (nhcdm.pdf) Section 2.11, pp.2-25 to 2-26 (the 15-20 minute nap recommendation is on p.2-25; the caffeine-delay and 'only safe cure is sleep' wording are on p.2-26)

Many drivers mistakenly rely on coffee, music, or fresh air to push through fatigue on long hauls, but these only mask the symptoms temporarily. Understanding that sleep is the only real fix helps drivers plan rest breaks proactively instead of fighting fatigue until it becomes dangerous.