Heraclitus wrote, “No man ever steps in the same river twice, for it's not the same river and he's not the same man.” I've always thought this saying applied to knowledge. Depending on your circumstances, a book can be perfect or useless. But I'm thinking of this saying in terms of life now. At different points in time, you're ready for different things. You might be ambitious and extroverted when you're young and introspective when you're older.