MK24 - 4th class and 5th class

Today we make a still life. The teacher has arranged a collection of objects for us to choose from. The lesson starts as usual. To make a couple of sketches in charcoal from different perspectives. I am having a hard time finding a place in the circle of easels. We're a group of 15 and when one arrives late - like I usually do - there's not a whole lot of room left. But after a while I find my groove and manage to make some satisfying sketches.
This is what the work in progress looks like:

I enjoy doing this more than I thought in advance. The teacher gives helpful advice. She says: work on the overall painting, step back regularly and don't lose yourself in details. She thinks the dark background is a cool choice.
In the next lesson we finish the painting. I have overworked the white pot and I am quite dissappointed. I think I liked it better when it was not finished. The teacher remarks that this is a common problem of artists; when is it done? when should you stop?