When doing research, there are days when you know you’ve made a lot of progress. And then there are days when you don’t know you’ve made a lot of progress, but you have.
It’s not that you got a lot done on that day. It’s more that some instinct has made you change direction.
It then usually takes another day or more to realize that you had turned a crucial corner, and are now heading the right way. After all, if you are walking in the wrong direction, you won’t get to where you want to go any sooner by walking faster.