The following is an excerpt from the book "Can You Trust God"

Notice that God’s promise is that he will keep us in perfect peace, but it is based on our minds staying
focused on him and trusting him. I can’t accuse God of not keeping me in peace when I refuse to keep my mind on him and refuse to trust him. The following verse is a promise.

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

If I read this verse only, I could easily believe that God will protect my heart and mind with his peace without
any responsibility of my own. I could confess this verse daily and tell everybody that I am claiming this scripture and still experience no peace. I must understand that it is based on my obedience to the verses before and after this one. I am commanded not to worry and to make all requests known to God accompanied with thanksgiving. If I couple this with consistent thinking about things that are true, honest, just, pure, lovely, and of good report, virtuous, and praiseworthy, then God will fulfill his obligation in garrisoning my mind with his peace.

Philippians 4:8 (KJV)
8 Finally, brethren, whatsoever things are
true, whatsoever things are honest, whatsoever
things are just, whatsoever things are
pure, whatsoever things are lovely, whatsoever
things are of good report; if there be
any virtue, and if there be any praise, think
on these things.

What if I refuse to think on these good things? Would it be legitimate for me to accuse God of not guarding
my heart and mind with peace? I know this is a rhetorical question, but we must always check the Word to see what our responsibility is so that God can fulfill his. We are so blessed to be under the domain of a righteous sovereign who obligates himself to fulfill his Word.