It is impossible to preserve peace of soul unless we watch over our minds - that is, unless we repel every thought unpleasing to GOD and, contrariwise, cling to those thoughts that are pleasing to HIM. Look into your heart and see what is happening there - do you find peace or not? If not, examine yourself to know what has transgressed. If we are to have peace of soul, we must live soberly, for our bodies, too, can cause us to lose grace. We must not be inquisitive - we should not read newspapers or secular books which lay waste the soul and bring about faint-heartedness and confusion. Do not criticize others. (People will often speak ill of a man without knowing him, whereas, in fact, in his mind, he is like the angels.) Do not seek to know what does not concern you: have thought only for the task set by your startzy, and the LORD will then succour you with HIS grace because of your obedience, ande you will witness in your soul the fruits of obedience, which are peace and unceasing prayer.
Living in a Community, we more often lose grace because we have not learned to love our brethren according to the LORD's commandment. If your brother offend against you, and you feel anger, or you condemn or detest him, you will find that grace has fled and peace departed. To have peace of soul we must school ourselves to love the man who has offended us, and forthwith pray for him.
There can be no peace for the soul unless she pray the LORD with all her might the gift of love towards all men. The LORD said, "Love your enemies," and if we will not love our enemies, we shall know no peace in our souls. At all costs, we must strive after obedience, humility and love: otherwise all our spiritual feats and vigils will count for nothing. A certain staretz had this vision: he saw a man pouring water into a trough, the bottom of which was all holes. The man laboured, but the water always ran out and the trough did not fill. So it is with us: we may live in a state of constant endeavour, but if we neglect this or that virtue our souls remain a desert. --St. Silouan the Athonite