One thing that stands out to me in the Bible is the description of the apostle Paul's "second missionary trip." It's in Acts 14. He and Barnabas go back to visit the churches they had formed on their first trip. Only two things are reported about that trip. They appointed elders in each of the churches, and they told them, "It is through many trials that we enter the Kingdom of God."

Luke, who wrote the book of Acts, summed up their trip with only one message: it's going to be difficult; don't give up. A lot of the New Testament is devoted to saying that it is worth it to continue to the end. In fact, the entire book of Hebrews exhorts Jewish believers to stick out the difficulties and not return to Judaism.

Perhaps the only sermon we have from the second century is called "2 Clement." Nowadays it is generally just called "An Early Christian Sermon" because almost no one believes the anonymous sermon was actually written by Clement of Rome. That sermon also focuses on continuing in the faith, and you can read it at https://www.christian-history.org/2-clement.html

Merry Christmas to all of you,