(1) Thinking is such a hard pastime that the majority of people opt to never give it a go.
(2) When this professor decides to sit and think about a matter, my mind inexplicably wanders. From one thing, to everything. Eventually, it comes full circle. That’s when I decide the original matter really isn’t worth thinking about anyway. [I know: it’s not really a proverb. But that’s all I could do, dadblameit!]
(3) I think, we think. But they don’t think! [Merlin usually says this when he’s teaching. He lectures about animal feet, believe it or not.]