Stamina is defined as the physical or mental capability to perform something at the highest level for prolonged periods of time. Stamina is considered to be one of the most vital components in health and fitness.
Stamina comes in two forms, physical and mental.
Your physical stamina measures the ability of your heart and lung muscles to function efficiently and supply the needed amounts of oxygenated blood during long and intense periods of physical activity.
On the other hand, your mental stamina defines the ability of your mind to push through difficult circumstances and think clearly for a very long time without fatigue.
You need both physical and mental stamina because they work hand in hand. For instance, even if your body is well-conditioned, but your mind is fatigued, and vice versa, it can be difficult to succeed in, let alone finish a particular task.