> If I focused on my weaknesses, I'd still be working on my handwriting.

He wasn't asking you concentrate on all your weaknesses. Prioritize your weakness based on their importance and then eliminate them.

for example: If you don't know how to drive a car- that is a weakness, and driving is a very important skill, so you try to eliminate it.

(This is just an example. You can always argue by saying that you can hire a person to drive the car for you, but think about other high-priority weakness you have)