Jesus commands us to bear the fruit of holiness and evangelization, or we will be "cut down" (Lk 13:9) and "thrown in the fire and burnt" (Jn 15:6). In other words, we can go to hell for not living and sharing the faith.
Jesus is so strict about this because He is Love (1 Jn 4:8, 16) and therefore wants all people to be saved (1 Tm 2:4) from sin, death, and hell by believing in Him. Because of sin, the whole world is under condemnation to fear, slavery, self-deception, guilt, self-hatred, anger, and violence. Jesus, in His love, has died on the cross and risen from the dead to save us from this terrifying condemnation. Then, He made us missionaries and messengers of this good news. In His love, He must insist that we give the following message to a condemned world: "There is no condemnation now for those who are in Christ Jesus. The law of the Spirit, the Spirit of life in Christ Jesus, has freed you from the law of sin and death" (Rm 8:1-2).
If we love God and other people, we will be missionaries. If we do not love, we are "among the living dead" (1 Jn 3:14). Love, and bear the fruit of evangelization.