Worry springs from not being convinced of a sovereign God's absolute love for you. Worry disappears when you realize that God loves you unfailingly and will let nothing interrupt His plans for your good.
The amount which you understand the gospel is measured by your ability to be joyful in all circumstances. If you grasp what a treasure the presence and acceptance of God are, then even when life goes really wrong you will have a joy that sustains you, because you’ll recognize the value of what you have in Him. When life punches you in the face, you’ll say, ‘But I still have the love and acceptance of God, a treasure I don’t deserve.’ And the joy you find in that treasure can make you rejoice even when you have a bloody nose. You have a joy that death and depravation cannot touch.