Rabbi Simcha Bunim of Parshischo said that every person should have two slips of paper in his pocket.
On one should be written: “The world was created for me.”
On the other should be written: “I am but dust and ashes.”
The trick is to have the wisdom to know which slip of paper to read at the right time.
Sources: Simchas Yisroel, p.41; Rabbi Zelig Pliskin’s Gateway to Happiness, p.126