Isaiah 26:3 Thou wilt keep him in perfect peace, Whose mind is stayed on thee: Because he trusteth in thee.
In the storms that will come in your life on the mission field only one thing will keep you going and that will be if you learn to think on these things.
Philippians 4:8 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.
We are to stay our mind on Him. He then gives perfect peace. That is a strong modifier. Perfect peace is the peace that passes all understanding.
Philippians 4:7 And the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus.
We are to set our affections on things above
Colossians 3:1 If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God. 2 Set your affection on things above, not on things on the earth.
Anybody can have peace when all is going right but only God gives peace when all is going wrong. Stay your mind on Him and trust Him.