It is possible to undergo a fiery trial because of one’s own folly, but Peter in the present context is not instructing his readers to “rejoice” at that. He is instead asking his readers to rejoice in those sufferings that result from their allegiance to Christ (Matthew 5:11–12; contra Luke 6:26).
13 But rejoice insofar as you share Christ’s sufferings, that you may also rejoice and be glad when his glory is revealed.