Let nothing disturb you,
Let nothing frighten you,
All things are passing;
God only is changeless.
Patience gains all things.
Who has God wants nothing.
God alone suffices.St. Teresa of Avila, whose autobiography inspired Edith Stein to convert to Catholicism, be martyred at Auschwitz, and eventually be canonized a saint (Saint Teresia Benedicta of the Cross), wrote this prayer in the 16th century and carried it in her prayerbook until her death in 1582.
H/T: bmck