"Let not your heart be troubled: ye believe in God, believe also in me."
"...be wise, and guide thine heart in the way....."
"Keep thy heart with all diligence; for out of it are the issues of life."
"...commune with your own heart upon your bed, and be still. Selah."
"Be not so troubled as to be put into a hurry and confusion, like the troubled sea when it cannot rest. He does not say, "Let not your hearts be sensible of the griefs, or sad because of them " but, "Be not cast down and disquieted," "Though the nation and city be troubled, though your little family and flock be troubled, yet let not your heart be troubled.
Keep possession of your own souls when you can keep possession of nothing else.
The heart is the main fort; whatever you do, keep trouble from this, keep this with all diligence. The spirit must sustain the infirmity, therefore, see that this be not wounded. "You that are my disciples and followers, my redeemed, chosen, sanctified ones, however others are overwhelmed with the sorrows of this present time, be not you so, for you know better; let the sinners in Zion tremble, but let the sons of Zion be joyful in their king." Herein Christ's disciples should do more than others, should keep their minds quiet, when every thing else is unquiet."
"Those that rightly believe in God will believe in Jesus Christ, whom he has made known to them; and believing in God through Jesus Christ is an excellent means of keeping trouble from the heart. The joy of faith is the best remedy against the griefs of sense; it is a remedy with a promise annexed to it; the just shall live by faith; a remedy with a probatum est annexed to it. I had fainted unless I had believed."
"Keep out bad thoughts; keep up good thoughts; keep the affections upon right objects and in due bound..... there are many ways of keeping things—by care, by strength, by calling in help, and we must use them all in keeping our hearts."
"One good means of preventing sin...is to be frequent and serious in communing with our own hearts: "Talk with your hearts; you have a great deal to say to them; they may be spoken with at any time; let it not be unsaid."Commune with your hearts; examine them by serious self-reflection, that you may acquaint yourselves with them and amend what is amiss in them; let your thoughts fasten upon that which is good and keep closely to it. Consider your ways, and observe the directions here given in order to the doing of this work well and to good purpose. "Choose a solitary time; do it when you lie awake upon your beds. Before you turn yourself to go to sleep at night," "examine your consciences with respect to what you have done that day, particularly what you have done amiss, that you may repent of it. When you awake in the night meditate upon God, and the things that belong to your peace."
Matthew Henry on John 14, Psalm 4, and Proverbs 4.