If a person internalizes the awareness that everything the Almighty does is for the good, he will not worry.
The story is told of a poor man who devoted his life to Torah study, and although he lived a life of poverty, he was constantly happy. One day at noon he began to cry because he feared he had made a blessing in vain. During the morning service he recited the blessing that "the Almighty has met all my needs." But on this day he had not yet eaten anything and had no money to buy food.
Then he realized poverty itself was his specific need. That was his life challenge: to see if he could live properly and righteously amidst his difficulties.
(Derech Slulah, p.10; Rabbi Pliskin's Gateway to Happiness, p.165)