Someone who is very clumsy because of severe neurological problems could, by effort, get somewhat better, but even with a lot of effort he will still be clumsy, just less clumsy.

The fact that something isn't changeable by investing effort doesn't mean that it isn't changeable by another strategy. Sometimes the key to change is investing less effort.

Biological issues and mental issue also also often interlinked. Making it part of your identity that you can't do something for biological reason X can often make change more difficult.