3 Blessed be the God and Father of our Lord Jesus Christ! According to his great mercy, he has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead, 4 to an inheritance that is imperishable, undefiled, and unfading, kept in heaven for you, 5 who by God’s power are being guarded through faith for a salvation ready to be revealed in the last time. 6 In this you rejoice, though now for a little while, if necessary, you have been grieved by various trials, 7 so that the tested genuineness of your faith—more precious than gold that perishes though it is tested by fire—may be found to result in praise and glory and honor at the revelation of Jesus Christ. (1 Peter 1:3-7 ESV)
When God saves a person, he or she is changed forever because they are new creations. However, they are not at the spiritual maturity level that God desires for His people. Therefore, from that point until they go home to be with their Lord, all genuine Christians will go through a series of tests and trials that put pressure on their faith. This pressure is spiritual, but the circumstances applying it come from all directions and sources. The Apostle Paul had a thorn in the flesh that put his faith to test to the point that he implored the Lord to take it away.