And the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus. – Philippians 4:7

The presence of thanksgiving in the heart together with prayer is productive of peace. “In everything by prayer and supplication with thanksgiving let your requests be made known unto God, and the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus.” Now that peace, that conscious calm, that divine serenity, which is described as the peace of God, is not produced by prayer alone, but by prayer with thanksgiving. Some men pray, and therein they do well; but for lack of mixing thanksgiving with it their prayer agitates them, and they come away from the closet even more anxious than when they entered it. If they mingled in their petitions that sweet powder of the merchants, which is called praise, and mixed it after the art of the apothecary, in due proportions, the blessing of God would come with it, causing repose of heart. If we bless our gracious Lord for the very trouble we pray against; if we bless Him for the very mercy which we need, as though it had already come; if we resolve to praise Him whether we receive the boon or not, learning in whatsoever state we are therewith to be content, then “the peace of God, which passeth all understanding, will keep our hearts and minds by Christ Jesus.” Brethren, as you value this divine rest of spirit, as you prize constant serenity of soul, I beseech you, mingle praises with your prayers.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1469.cfm