... mostly in pottery anyway.

The analog nature of the wiring of the mammal brain prevents us doing things perfectly or repeating things exactly the same. Practice does not make perfect, but it makes better. The human body is far from perfect (and needs constant maintenance) and is impermanent.

In working with clay in pottery class the last few months, perfection has come up, at least for me. I'd be happy with making something that's a "keeper", but it takes time learn the skill to make pottery that's balanced, symmetrical, etc., especially on the wheel.

Even after the object is made there are still opportunities for things to go awry. The objects can warp, crack, or explode in the kiln. After that, the glazing introduces another set of variables and result in a runny, crackled, or pitted glaze or all of those. In some circumstances, those things are the effects of interest, but there's where the skill comes in again.

Add up the imperfections in the clay-forming process, then add the firing modifications, then add the glazing wildness, and the final object can be pretty far from the initial vision. I asked the teacher about this progression and he said that it's the nature of working with clay, but as you gain experience your control over some of the variable increases. Mostly in the form of better ability to form the clay. What happens in the kiln is still a wild card, but you learn to prepare for that.

Art is often a mix of skill and understanding, both of which come from experience, and pottery seems to me to need a lot of both.