Although I've spent more than 30 years as a programmer, before that I spent 8 years as an art major so I know a little bit about how non-artist types steer away from this kind of thing. That said, there are a few things that might help. One of my favorites is 'I can't draw a straight line...' well, neither can I (nerve damage and age)---when I need one, I use a ruler. Another is the usual comparison to some great artist, Rembrandt or the like. If you actually look at them you usually find out that what they can (or could) do breaks down into two areas---that which can be learned and talent. Can't do a damn thing about talent, you have to be born with that, but learning (which amounts to a bit more than 80% of what most think of as good art), that is a matter of teaching and practice. Best way to get to the goal of decent artwork is to stop telling yourself you can't do it and pick up whatever tool happens to be handy and have a go at it.