The grindstone sharpens through friction, read as hard work and repetitive effort. The old phrase about a nose to the grindstone colours it with diligence, and sometimes with weariness.
Where in your waking life have you met something like this lately?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.