1 Peter 1:6

6 In this you greatly rejoice, even though now for a little while, if necessary, you have been distressed by various trials,

Peter tells them that they should be glad in their sure salvation and in the protection God will give them, even in the trials they are having to endure. But they are to know that the trials will only last for a little while (Some of these trials were from their persecution that came during the reign of Nero, who blamed the burning of Rome on Christians.).