"Worry exhausts vitality. True, all good in life costs. Virtue goes out of us in everything we do that is worth doing. But for normal, healthy action nature provides. There is recuperative energy enough to supply the waste. The fountains are filled as fast as it is worn away. Worry, however, is abnormal and unhealthy. It exhausts vitality more rapidly than nature can reinforce it. It is like friction in machinery, and grinds away the very fibre of life. Worry, therefore, both impeded progress and makes work unduly costly and exhausting. One neither accomplishes so much nor does it so well, while the outlay of vitality is greater.
The ideal theory of life is, therefore, work without worry. At least, this certainly ought to be the ideal for a Christian. We have an express command not to be anxious about anything. Our whole duty is to do the will of God and leave in his hands the outworking of circumstances, the shaping and overhauling of all the complicated network of influences, so as to bring about the right results. The working plan for a Christian life is clearly laid down in our Lord’s words: “Seek ye first the kingdom of God, and his righteousness; and all these things shall be added unto you.” “Take therefore no thought for the morrow: for the morrow shall take thought for the things of itself.” This ideal leaves no place whatever for worry. It requires single-hearted devotion to the interests of Christ’s kingdom, the elimination of self and self-seeking, uncompromising loyalty to the principles of righteousness, and the faithful and energetic doing of duty, — all duty, without regard to pleasure or cost. This is all the human part. Then God will look after the outcome; will take care of us and of the results of our acts. It is the function of faith, when we have done what we can, to put all into the divine hands, giving ourselves no anxiety, while we go forward in peace and confidence to the next duty that awaits.
It is said of a Christian man, who has risen from a humble station to great national prominence that his motto has always been: “Do the very best you can, and leave the rest to Providence.” This is nothing more or less than the putting into plain, crisp Saxon, our Lord’s counsel already quoted. If we would all get this bit of practical heavenly wisdom out of our New Testament and into our daily life, it would not only greatly increase our working capacity, and consequently make us more successful, but it would also largely enhance our happiness."My note: To be technical, I'd say our motto should be to lean on Providence from the beginning of any endeavor and do our best as we trust in the Lord and leave the results to Him." But, that's a mouthful.