Quite frankly, I think that's a load of crap.
Regardless of what creative field you're in, you shouldn't be afraid to create something that will never see the light of day. You should make art, pictures, music, whatever just because you want to. You should do it because the value of the art is not in what other people give it, but what you as the artist give it. The value of my photography is high to me because I enjoy taking pictures! Sure, getting complements and/or cash is nice... but the reason I really like photography is because it provides me with a creative outlet - it is something I enjoy doing, not just something I enjoy selling.
In the spirit of messing around, I'll show you this. I pulled a mediocre picture into photoshop and just went nuts. I enjoyed doing it and it got my creative juices flowing again. I know I'll never sell a print of this. I also understand that even though I won't make a cent off this image, that doesn't make it worthless.
