Stress, worry, and anxiety simply come from projecting your thoughts into the future and imagining something bad. This is focusing on what you don't want! If you find that your mind is projecting into the future in a negative way, focus intensely on NOW. Keep bringing yourself back to the present.
Use all of your will, and focus your mind in this very moment, because in this moment of now there is utter peace.
The Secret Daily Teachings (ed. Simon and Schuster, 2013) - ISBN: 9781471132278