> Drive is something we can choose and cultivate.

That sounds like hybris. I am not disagreeing that you can alter it to a degree, but it is certainly not something you choose. Just think about how you feel when you are ill and now think of people with allergies for example, that can always feel ill depending on circumstances.

These limits exist always and they are different from person to person and these limits are not always set by (obvious) illnesses, but by the body in general.

edit: limit => limits