Clay is plastic, and by plastic we mean that it can be molded and shaped into a desired form for a specific function or purpose.
But clay has memory.
We can get all technical with the terms and scientific reasons why clay has a memory, but let's be simple about it.
Clay is basically dirt and water and we move and shape it through various processes to make it into what we want. Those elements form paths and bindings that reinforce the shape of the piece and hold it in place.
So like the rain forms rivers, we form mugs and bowls. And when the rains change and the river changes course it leaves a remnant of the old path and the flow of the river is never quite the same again. So too does clay remember if you change it's shape too much that it was once different.
While it is just mud and we can mush the whole thing back into a ball, wedge it a bit, and start from scratch, it is something to be aware of while in the process of forming the clay to begin with.
Clay and people are not so different. We are shaped and molded by the forces around us, they leave impressions on our surfaces and guide us down different paths. Sometimes we have to change the path, tighten up or loosen up a little, and sometimes we have to completely turn around and start over.
Until the clay meets the kiln it's design isn't permanent, so think about the clay. What memories does it hold? Are they good? Bad? Have those forces pushed and pulled too much? Too little? Is it ready for the final process to become complete or do we need to go back to the starting point?
Whatever is decided we must try not to get upset, because while clay has memory it also can have a mind of it's own. And some days it just doesn't want to work the way we want it to, we must be patient, sometimes it's better to leave it alone and come back once it's settled down a bit.