Faith is being . . . certain of what we do not see. (Hebrews 11: 1)
Genuine faith puts its letter in the mailbox and lets go. Distrust, however, holds on to a corner of the envelope and then wonders why the answer never arrives. There are some letters on my desk that I wrote weeks ago, but I have yet to mail them because of my uncertainty over the address or the contents. Those letters have not done any good for me or anyone else at this point. And they never will accomplish anything until I let go of them, trusting them to the postal service.
It is the same with genuine faith. It hands its circumstance over to God, allowing Him to work. Psalm 37: 5 is a great confirmation of this: “Commit your way to the Lord; trust in him and he will do this.” He will never work until we commit. Faith is receiving— or even more, actually appropriating— the gifts God offers us. We may believe in Him, come to Him, commit to Him, and rest in Him, but we will never fully realize all our blessings until we begin to receive from Him and come to Him having the spirit of abiding and appropriating.
~from Days of Heaven upon Earth
Dr. Payson, while still a young man, once wrote to an elderly mother who was extremely worried and burdened over the condition of her son. He wrote,
You are worrying too much about him. Once you have prayed for him, as you have done, and committed him to God, you should not continue to be anxious. God’s command, “Do not be anxious about anything” (Phil. 4: 6), is unlimited, and so is the verse, “Cast all your anxiety on him” (1 Peter 5: 7). If we truly have cast our burdens upon another, can they continue to pressure us? If we carry them with us from the throne of grace, it is obvious we have not left them there. In my own life I test my prayers in this way: after committing something to God, if I can come away, like Hannah did, with no more sadness, pain, or anxiety in my heart, I see it as proof that I have prayed the prayer of faith. But if I pray and then still carry my burden, I conclude my faith was not exercised.
Cowman, L. B. E.; Reimann, Jim (2008-09-09). Streams in the Desert: 366 Daily Devotional Readings (p. 169). Zondervan. Kindle Edition.