Because learning something new takes time.

It’s easy to repeat old mistakes, it’s sure easier than learning something new.

Learning something new, until you become a professional, takes a lot of time.

So it’s better to grind a thing you are already good at.

Because the grind is what makes you better.

Imagine I would pick up a pencil and started to draw – my drawings sure wasn’t as good as my text. And who knows, maybe drawing wouldn’t work out too.

It’s better to grind a good thing.