The gospel of the kingdom can take on “happy” tones if we are not careful. Notice this “gospel” text:

34 Then he called the crowd to him along with his disciples and said: ???If anyone would come after me, he must deny himself and take up his cross and follow me. 35 For whoever wants to save his life will lose it, but whoever loses his life for me and for the gospel will save it. 36 What good is it for a man to gain the whole world, yet forfeit his soul? 37 Or what can a man give in exchange for his soul? 38 If anyone is ashamed of me and my words in this adulterous and sinful generation, the Son of Man will be ashamed of him when he comes in his Father’s glory with the holy angels.???

The gospel is something that summons a person to the core of that person’s being. It summons that person to die. “When Jesus calls a man, he bids him come and die” — so the famous (paraphrastic) translation of Bonhoeffer.
Gospel preaching or gospel summoning here is the summons to a cross.
Jesus summons through his gospel to give it all up for the gospel (v. 35). Losing one’s life for Jesus, or for the gospel — which are nearly the same thing here!, is the way one “saves” one’s life.
Giving it up for the gospel means surrendering one’s opportunity to “gain the whole world” (36). The “soul” is what matters here.
And giving it up for Jesus means Jesus will honor and own that person at the Final Judgment; holding it back means Jesus will be ashamed of that person at that Day.
To embrace the gospel is to embrace Jesus; to embrace Jesus is to embrace the Cross; to embrace the gospel means we embrace the Cross. There is no gospel without the Cross of Jesus. None. Gospel response is death to self. No to self and Yes to Jesus, the Jesus who painted the way in the Cross.