For a short half-hour show you kind of need to do that if you want to get good results; not a lot of time to take a step back and look at things, and you also want to actually have a finished painting after 30 minutes (and not 24 or 35).

The general message still holds I think: "you're painting for your own enjoyment, there is no 'good' or 'bad' and the only thing that matters is that you're having fun".