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.
Of course you can be more driven (there is of course a limit but most are far from it). I have done it I used to be content with where I was in life. Made decent money, family, friends and hobbies.
But I decided that I wanted more so I let my hobbies grow a bit and changed employer. Sure I'm not a million miles from where i was but I'm not in the same place.
Once I took the first steps the next got easier and I started to look for more opportunities. Find your first step, it should be small but in the right direction. Ask to take lead on something at work or push yourself in your hobby.
What I think everyone with kids should have as one of their goals is to get them one step up the ladder. Give them a slightly better chance than you had. Most successful people have successful parents, very few start from zero. My parents were middle class but I'm upper middle class.
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