I've done it. I'll admit it.
I've said tons of times, "yeah, it's not very good but..."
"I was just playing around..."
"It's a rough sketch..."
I know a lot of other artists who downplay their art, either before someone sees it, or after someone compliments it.
Our teachers in college warned us about the dangers of doing it in front of possible recruiters, because selling yourself short means other people see your work through that lens.
And that's a very good reason not to do it.
Another good reason is that beating yourself up over every little mistake you made is extremely demoralizing, and enough of it builds a wall that makes getting work or even practice done impossible.
But another reason hit me today – when I say "Oh it's just a rough sketch, I know it's not very good", does the person I'm talking to, or someone overhearing me, or someone on the internet reading that – do they know that I went to 4 years of animation school, have done years of life drawing, have taken painting classes, look up stuff online, etc, etc, etc...?
Not always. And for artists just starting out, hearing someone say their art isn't very good when it looks like it's above their skill level is hugely demoralizing. I remember hearing someone (who I later found out had decades of experience) talk about how crummy their painting was, and thinking "wow, I'm never going to make it as an artist."
So even if I think my work has miles to go, even if I can see all the little spots I ƒüç˚é∂ up, I'm not going to preface showing or respond to comments about my work with any self-deprecating comments. I can just start with "This is something I'm working on" or follow-up with "I really appreciate you saying that, it's nice to hear."I can say something more neutral or not at all.
I could even say that I like it.