Try to put well in practice what you already know; and in so doing, you will in good time, discover the hidden things which you now inquire about. Practice what you know, and it will help to make clear what now you do not know.
Rembrandt took his own advice and painted many pictures of old age, and especially of his own aging.
Jonathan Jones, who writes about art for the Guardian, lists many painters whose attitude towards old age was either dismissive or negative. However, Rembrandt, he says, is “an artist to grow old with.”
“His unrivaled and sustained self-portraiture shows how he himself changed with time. As he ages, he sees himself more intimately: he stops pretending to himself. To compare his self-portraits at the ages of 34 and 64 is to witness someone grow in suffering and sorrow and, perhaps, wisdom. At 34 he looks proud, at 63 he simply looks human.”