Even by the time Peter wrote this letter, some were sick of waiting for Jesus’ return and started to doubt it would ever happen:
2 Peter 3:3-4 Most importantly, I want to remind you that in the last days scoffers will come, mocking the truth and following their own desires. They will say, ‘What happened to the promise that Jesus is coming again? From before the times of our ancestors, everything has remained the same since the world was first created.’
But Jesus will come back, and when he does, no one will be expecting it:
2 Peter 3:10 But the day of the Lord will come as unexpectedly as a thief. Then the heavens will pass away with a terrible noise, and the very elements themselves will disappear in fire, and the earth and everything on it will be found to deserve judgment.
But believers can look forwards to His return. On that basis, we should live as best we can:
2 Peter 3:13-14 But we are looking forward to the new heavens and new earth he has promised, a world filled with God’s righteousness. And so, dear friends, while you are waiting for these things to happen, make every effort to be found living peaceful lives that are pure and blameless in his sight.