Mark 1
14 Now after John was arrested, Jesus came into Galilee, proclaiming the gospel of God, 15 and saying, “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.”
When the Kingdom of God is at hand there are only two things we can do to respond. Repent and believe in the gospel. You can choose to not repent but you will miss out in what the Kingdom of God has to offer.
The gospel declares that everything we need is found in Christ. To not live in the gospel means I am holding on to something else that is not Christ and the problem with that is that it won’t fulfill and it won’t give life.
So you have to make the decision to repent of holding onto something that is not Christ and believe that everything I need is found in Christ alone.