One of the things I like most about teaching art classes to kids between ages five and thirteen is that their mistakes are so obvious to me.
One girl's fence got bigger as it went farther away from view. She knew that the parallels of the fence were at an angle, but she couldn't wrap her mind around that angle.
I had the same problem wrapping my mind around that angle convergance problem when I recently did a painting involving four or five staircases. I knew something was wrong but I couldn't figure out what. I was trying to give you two horizon lines!
If you don't know what these two mistakes are at all, here's a quick tutorial: in One-Point Perspective.
Then there was the boy who was mistaking lots of short, tiny brushstrokes for details.
And there's me, so obsessed with getting the lines right I've been forgetting to be picky about getting the colour exactly right.
Variety is the spice of Life. If you think that's a lame cliche, then don't use variety in your paintings, but follow the example of Manzoni and his 'Achromes' . Manzoni.
But it would be better if you looked him up in a library; I'm not entirely happy with what the internet is explaining.
We all make mistakes, it's just easier to see the ones you've moved past, which is why I teach little kids art but am still at ECIAD art school. I could be cheesy and say I learn more from my students than they do, but what I'm going to say is that I think I get more giggles out of it than they do.
Like the girl that, when asked to pick a relaxing colour, chose florescent pink.