When I was a teen a read somewhere this quote from Rabbi Simcha Bunam, although it was unattributed at the time (it might have been a character in a book, it might have been an inspirational quote on a card). I liked the quote so much it lived on the wall in my room for a long time.
Keep two truths in your pocket and take them out according to the need of the moment. Let one be “For my sake the world was created.” And the other: “I am dust and ashes.”
—Rabbi Simcha Bunam