"Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee." (Isaiah 26: 3)
He is our life, and before we rest in this truth, we need to understand that He is the fullness of all things. In his letter to the Colossians, Paul could not expound on Jesus' full preeminence any better:
"15[Jesus] is the image of the invisible God, the firstborn of every creature: 16For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him: 17And he is before all things, and by him all things consist. 18And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence. 19For it pleased the Father that in him should all fulness dwell; 20And, having made peace through the blood of his cross, by him to reconcile all things unto himself; by him, I say, whether they be things in earth, or things in heaven." (Colossians 1: 15-20)
He holds all things together, including you and me.
Yet that is not His greater claim to fame:
"21And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled 22In the body of his flesh through death, to present you holy and unblameable and unreproveable in his sight: 23If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; whereof I Paul am made a minister;" (Colossians 1: 21-23)
We have been redeemed from sin and death through His death and resurrection. To create, God only had to speak. To redeem all of us, God had to bleed, and bleed He did through His Son Jesus.
The question which brings us back to peace every time is not about fixing our thinking, but remembering that He is there, and He is there for us, regardless of what we are thinking and feeling.
The problem was not what I was doing or not doing, but that I was not seeing more of Jesus, growing in grace and knowledge of the Lord (2 Peter 3: 18)
God no longer invites us to look at ourselves, but to look at His Son:
"But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord." (2 Corinthians 3: 18)
The issue is not thinking differently, or doing more, but gaining a greater revelation of Jesus.
How can our minds not be stayed on Him? He covers every inch of eternity, and wherever we go, we know that He is already there.
The issue was not me, but seeing more of Him.
The issue was not keeping my mind thinking or feeling a certain way.
The revelation that He is not going anywhere, and that He is committed to taking care of me every step of the way - that brings me great peace.
There is no reason to ask questions like: "What about tomorrow?" as if tomorrow is too big for God.
There is no reason to ask: "How shall I do. . ." since He is our life, and He is living and moving within us and willing in us both to desire all things.
In fact, the language of the verse in the Original Hebrews speaks not actively of our resting on Him, but rather Him causing us to rest in Him.
"Come unto me, all ye that labour and are heavy laden, and I will give you rest." (Matthew 11: 28)
The Greek literally reads: "I will rest you."
We need to understand that Jesus is a living Person, our God and a Savior who does not stop saving us.
We do not come to Him just as a rest from our sinful former selves and receive His Life. He invites us to come to Him every day and rest in Him, and Let His life take over.
This rest is hard for us if we do not see that He is already taking care of all things for us. The idea of wondering whether He will be there for me or not just makes no sense when you see Him right in front of you, and you know that He cares for you (1 Peter 5: 6-7).