Peter writes to exiled believers who are facing great persecution. He reminds them of who they are and whose they are. Even though they might be facing all kinds of trials and hardship they can have joy because their faith is anchored in the one who remains the same.
In verse 6 he says to them “In all this you greatly rejoice,though now for a little while you may have had to suffer grief in all kinds of trials.”
As believers we will face trials of all kinds but we can greatly rejoice because the crown that awaits us is sure. God holds for us that which will bring us great joy for eternity. Our temporary sadness will be overshadowed by the permanent joy God holds for us.