Without faith it is impossible to please God, no matter what else you may have (Heb.11:6). Eve's failure in the garden was a failure of faith. If she had only trusted in the perfect love and wisdom of God, when she was tempted by the attractiveness of that tree, even if she could not understand why a loving God would forbid her from eating it, then she would not have sinned. But once Satan had made her doubt God's love, she fell very quickly.
There are many things that God has forbidden for us too, and many prayers of ours that He does not see fit to grant. At such times we must trust in His perfect love and wisdom. Jesus trusted the Father on the cross even when He was forsaken. He did not say, “O God, why have You forsaken Me?" He said, “MY God.....", meaning thereby, “Even if I can't understand why You have forsaken Me, You are still My God". There was no reply from heaven to Jesus' query. But He died trusting. He said, "Father I commit My spirit into Your hands" (Luke 23:46). That is what it means to endure in faith until the end.
Jesus told Peter that Satan had requested for permission to sift him. This was similar to the way Satan asked God for permission to sift Job (in the Old Testament). Satan cannot do anything to us (even tempt us), without God's permission. But when Peter was going to be sifted, Jesus assured him that He would pray for him that his faith would not fail (Luke.22:31, 32). That is all that matters. Jesus does not pray that we should not be tempted, or that our health or wealth or job should not fail, but only that our FAITH should not fail.
Faith is therefore our most important treasure, in Jesus' eyes. If we have faith, then we will never be discouraged, even if we fail miserably, like Peter did. We will jump up (not just get up but jump up) and overcome Satan by the word of our testimony concerning the blood of the Lamb that cleanses us thoroughly when we turn from our sin and confess it to God (Rev.12:11). We must tell Satan that we have been cleansed by the blood of Jesus and that God does not remember any of our past sins any more (Heb.8:12). We have to tell that to Satan that, with our mouths, since he cannot hear our thoughts. Thus, we will overcome him, and he will flee from us.
“Do not rejoice over me, O my enemy. Though I fall I will rise. Though I dwell in darkness, the Lord is a light for me. He will bring me out to the light. Then my enemy will see, and shame will cover him who said to me, `Where is the Lord your God?' At that time he will be trampled down like the mire of the streets (under our feet)." (Micah 7:8-10).
We must boldly say at all times, "The Lord is my helper. I will never be afraid (of any man or demon or circumstance or anything) , for God has promised never to leave me nor forsake me" (Heb.13:6,5). That is the bold confession of our faith.