Agree with God, and be at peace.Job 22:21
In order to properly "agree with God, and be at peace," we must know Him as He has revealed Himself, not only in the unity of His essence and subsistence, but also in the plurality of His persons. God said, "Let us make man in our image"1—man must not be content until he knows something of the "us" from whom his being was derived.
Endeavor to know the Father. Approach Him in deep repentance, and confess that you are not worthy to be called His son; receive the kiss of His love; let the ring that is the token of His eternal faithfulness be on your finger; sit at His table and let your heart rejoice in His grace.
Then press forward and seek to know much of the Son of God who although He is the brightness of His Father's glory humbled Himself and became man for our sakes. Know Him in the singular complexity of His nature: eternal God, and yet suffering, finite man; follow Him as He walks the waters with the tread of deity, and as He sits down at the well tired in the weariness of humanity. Do not be satisfied unless you know much of Jesus Christ as your Friend, your Brother, your Husband, your all.
Do not forget the Holy Spirit. Endeavor to obtain a clear view of His nature and character, His attributes, and His works. Behold the Spirit of the Lord, who first of all moved upon chaos and brought forth order, who now visits the chaos of your soul and creates the order of holiness. Behold Him as the Lord and giver of spiritual life, the Illuminator, the Instructor, the Comforter, and the Sanctifier. Behold Him as He descends upon the head of Jesus, and then as He rests upon you.
Such an intelligent, scriptural, and experiential belief in the Trinity is yours if you truly know God; and such knowledge brings peace indeed.
1) Genesis 1:26