We become a true Christian when our mind is set on the will of God, more than on our own needs. God knows exactly what we need therefore we should not be of a doubtful mind(Luke 12:22-31). 22 And he said unto his disciples, Therefore I say unto you, Take no thought for your life, what ye shall eat; neither for the body, what ye shall put on.23 The life is more than meat, and the body is more than raiment.24 Consider the ravens: for they neither sow nor reap; which neither have storehouse nor barn; and God feedeth them: how much more are ye better than the fowls?25 And which of you with taking thought can add to his stature one cubit?26 If ye then be not able to do that thing which is least, why take ye thought for the rest?27 Consider the lilies how they grow: they toil not, they spin not; and yet I say unto you, that Solomon in all his glory was not arrayed like one of these.28 If then God so clothe the grass, which is to day in the field, and to morrow is cast into the oven; how much more will he clothe you, O ye of little faith?29 And seek not ye what ye shall eat, or what ye shall drink, neither be ye of doubtful mind.30 For all these things do the nations of the world seek after: and your Father knoweth that ye have need of these things.31 But rather seek ye the kingdom of God; and all these things shall be added unto you.
When we put our trust in the Lord, He in turn will keep us in perfect peace when our mind is stayed on Him(Isaiah 26:3-9). 3 Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.4 Trust ye in the Lord for ever: for in the Lord Jehovah is everlasting strength:5 For he bringeth down them that dwell on high; the lofty city, he layeth it low; he layeth it low, even to the ground; he bringeth it even to the dust.6 The foot shall tread it down, even the feet of the poor, and the steps of the needy.7 The way of the just is uprightness: thou, most upright, dost weigh the path of the just.8 Yea, in the way of thy judgments, O Lord, have we waited for thee; the desire of our soul is to thy name, and to the remembrance of thee.9 With my soul have I desired thee in the night; yea, with my spirit within me will I seek thee early: for when thy judgments are in the earth, the inhabitants of the world will learn righteousness.
The truth of Christ changes us as we are renewed with His words of hope. Even though our outward body is perishing our inward spirit will not, and will one day live eternally with God our Father!(2 Corinthians 4:14-18),(2 Corinthians 5:1).