Faith: Promise of Things Hoped For:
"Now faith is the assurance of things hoped for, the evidence of things not seen."
The word assurance means confidence or promise. If your replace "substance" with the words "confidence" or "promise" it helps us understand faith, which helps us to have faith during our trials:
"Now faith is the [confidence] of things hoped for, the evidence of things not seen."
"Now faith is the [promise] of things hoped for, the evidence of things not seen."
Works of Faith:
"God having provided some better things for them through their sufferings for without sufferings they could not be made perfect."
Trials Necessary for our Salvation:
President Brigham Young said, "Every trial and experience you have passed through is necessary for your salvation," ("Healing Power of Forgiveness," May 2007 Ensign, 68.) Also see "Suffering is Necessary."
Faith Made Perfect Through Works:
"What profit is it, my brethren, for a man to say he hath faith, and hath not works? can faith save him?"
"Therefore wilt thou know... that faith without works is dead and cannot save you?" (JST James 2:14,18).
James then asks this question in verse 22, "Seest thou how faith wrought with his works, and by works was faith made perfect?"
Gratitude and Joy of Trials:
"My brethren, count it all joy when ye fall into many afflictions; Knowing this, that the trying of your faith worketh patience. But let patience have her perfect work, that ye may be perfect and entire, wanting nothing." (James 1:2-4, italics are from the JST)
More Precious Than Gold:
Faith in Christ = Patience in Trials:
He "refused to be called the son of Pharaoh's daughter: Choosing rather to suffer affliction with the people of God, than to enjoy the pleasures of sin for a season; Esteeming the reproach of Christ greater riches than the treasures in Egypt...." (Hebrews 11:24-26)
Also see the related articles, "What is Faith?" and "Temptations and Trials."