An individual is described as when they have the endurance to engage in daily activities, as well enough reserve energy to handle added challenges.

The answer is physically fit

Explanation:

A physically fit person is able to carry out activities without unwarranted fatigue. Physical fitness include muscle strength and endurance, flexibility, body composition etc. A physically fit person normally gets proper nutrition, enough physical exercise  and rest. A physically fit person is generally healthy .

The argument is ineffective and can be improved significantly. First of all, he writes the claim in the first person. A formal persuasive essay should be in the form of third person. The author can improve his support by using less opinions and back-up his thesis with facts and evidence and does not take a strong stance on the conclusion clincher. The author also does not efficiently connect his essay. There is no cohesion and his diction is weak. He can improve it by using stronger vocabulary.