Being passionate and obsessive are two different things.

> Turn idle time into mental rehearsal

Any psychologist would bash your head with a book for following this.

It unironically is. Maybe if you can afford not working, it's fine, but with a regular job you simply don't have that much free time. In vacuum, there is a lot of it, in practice once you get a few commitments, it gets very challenging.

There are some tricks -- if you are already good at something, maintaining that good level is usually not that hard (you already know how and can recalibrate your level to the available time), but picking up new concepts is very time consuming.

I'd also say that the article talks about living through something, that's probably more involved than just passionate.