In fact, it is as difficult to appropriate the thoughts of others as it is to invent.

Genuinely taking on somebody else’s thinking is harder than it looks. Repeating a formulation is easy, while actually holding the idea, seeing what it rules out and where it fails, takes nearly the work of having had it yourself. This is why so much borrowed wisdom sits inert, quoted correctly and never used.

When something you read strikes you, do not just save it. Put it in your own words without looking, then find one situation in your own life it changes. If you cannot do either, you have the sentence and not the thought, and it is worth going back for the rest.