PSA: I didn't get the point of layers for way too long
So, I've been messing with digital painting for a while, and for the longest time I just ignored layers. I'd paint everything on one single layer like I was using real paint on a real canvas, you know? It seemed fine until I tried to fix the shading on this one portrait. I went to lighten the cheek, but I messed up and brushed right over the eye line I liked. Trying to fix that, I then wrecked the hair. It was a huge mess. I finally gave up and watched a basic tutorial where the person just turned off a layer to erase a mistake without touching anything else. My mind was totally blown. I felt so silly. It was like I'd been trying to build a house with no foundation.
Wait you painted a whole portrait on one layer. How did you even fix anything without ruining the rest. I get nervous if my sketch layer touches my color layer. That cheek and eye story actually hurts to read.
Actually, using one layer forces you to plan and commit to your choices. It makes you a more confident artist because you can't just hide mistakes behind layers. That pressure can lead to better work in the end.
Forget about right or wrong, it's about what you're trying to do. If you're doing a quick sketch to catch a feeling, one layer keeps it loose and fast. But if you're building up a detailed cityscape with glowing windows over a dark sky, layers let you test that glow without wrecking the whole building. It's just a tool, like picking a brush.