I disagree completely. I think investing and fitness can be paralleled almost to a tee.
Category 1 - Hardcore Freaks
You have your hardcore nuts who do it every day - regardless, it is their top priority, nothing gets in the way of them spending time on their passion. They get good at it, and it shows. It consumes them. They love talking about it, they live and breathe it.
Category 2 - Middle Wannabes
Then you've got your middle of the road wannabes who are glad they are doing something, know they are better than the great unwashed, but marvel at the hardcore nuts who seem to make the impossible easy. They yearn and crave to be up in category 1, but just can't / won't bring themselves to sacrifice the time and effort necessary.
Category 3 - Also rans
Then you've then got your 'also rans', who do the odd thing here and there, but it's no big deal to them either way. They really couldn't give a flying fig if they didn't do another thing for the next 10 years and are happy to simply cruise. Vast bulk of the population are in here.
Category 4 - Sloths
Then you've got your sloths. Hopeless, won't hear about doing anything to improve their lot in life and blame their condition (financial or physical) on anyone who is in finger pointing range. Think the whole thing is a complete waste of time and -- do you mind, get out of the way -- I'm trying to watch some American drivel on TV which is far more important.
I think the parallels between being good at investing and fitness are very strong indeed.
Being a category 4 in both disciplines, I speak from experience.