[rtodea]

We love the things that we are good at.

If you start with easy math problems (but not labelling them as "math problems", but as logic, smart puzzles) you can build up from there.

Consistency and frugality of options is important.

[singularity2001]

We love the things that we feel good at. Even if we are objectively better than most peers playing an instrument, if the teacher (parent) gives the impression that we are not good all motivation might dwindle.

On the other hand if the approach of the author gives a slight competitive edge, this might snowball for the reason you've given.