The gospel includes certain facts. For example, Christ died for our sins and rose from the dead. If we are in covenant with Jesus, we have eternal life.
However, the gospel also includes some less commonly known facts. For example, the book of Hebrews reveals that if a born-again person deliberately keeps sinning, there is no more sacrifice for those sins.
When we know all the facts of the gospel, we can stand with confidence in our salvation in Jesus.