Darning black socks with black yarn turned out to be really hard. In my efforts to see the individual threads I kept stretching the holes too wide, so when I was done with the darning it didn’t lie flat.

At some point I realized how stupid this was. Why was I making this so hard for myself? I picked up a yarn in a contrasting colour. And now I could see what I was doing! My darning on this third sock looks a lot more even and tidy than the first two I did before it.