May the Lord give you His peace
Let there always be a vigilant sentinel in your soul which will discover anything that might trouble or disturb your conscience. At its first alarm, seize your weapons to defend yourself. Remember that all these evils, and a great many others, no matter how formidable their appearance, are but imaginary for they cannot deprive you of any real good. Consider this fact. Whether God decrees or permits these things for the reasons given above, or for others which we should certainly consider equitable, they are hidden from our comprehension.
You will find it greatly advantageous to preserve a calm mind through all the events in your life. Without it, your pious exercises will be fruitless.
I am convinced that, if the heart is troubled, the enemy is ever able to strike us, and as much as he wishes. Moreover, in that state we are not capable of discerning the true path to follow, the snares that must be avoided to attain virtue.
The enemy detests this peace. For he knows that this is the place where the spirit of God dwells, and that God now desires to accomplish great things in us. Consequently he employs his most devilish means to destroy this peace. He suggests various things that apparently are good. It is a trap; you will soon discover that these desires will destroy the peace of your heart.
Source: Catholic Tradition.org
THE SPIRITUAL COMBAT, Dom Lorenzo Scupoli
TREATISE ON PEACE OF SOUL AND INNER HAPPINESS, Dom Lorenzo Scupoli
UNIFORMITY WITH GOD’S WILL, Saint Alphonsus de Ligouri