Sin has consequences. Serious sin has serious consequences – the loss of eternal life.
Jesus:
If your right eye causes you to sin, pluck it out and throw it away; it is better that you lose one of your members than that your whole body be thrown into hell. And if your right hand causes you to sin, cut it off and throw it away; it is better that you lose one of your members than that your whole body go into hell. (Mt 5:29-30)
"I am the true vine, and my Father is the vinedresser. Every branch of mine that bears no fruit, he takes away, and every branch that does bear fruit he prunes, that it may bear more fruit. You are already made clean by the word which I have spoken to you. Abide in me, and I in you. As the branch cannot bear fruit by itself, unless it abides in the vine, neither can you, unless you abide in me. I am the vine, you are the branches. He who abides in me, and I in him, he it is that bears much fruit, for apart from me you can do nothing. If a man does not abide in me, he is cast forth as a branch and withers; and the branches are gathered, thrown into the fire and burned". (Jn 15:1-6)
The pruning is chastisement. But if we do not abide in Christ, if we bear no fruit, we are cut off and burned,
Paul:
Do you not know that if you yield yourselves to any one as obedient slaves, you are slaves of the one whom you obey, either of sin, which leads to death, or of obedience, which leads to righteousness? (Rom 6:16)
For freedom Christ has set us free; stand fast therefore, and do not submit again to a yoke of slavery. Now I, Paul, say to you that if you receive circumcision, Christ will be of no advantage to you. (Gal 5:1-2)
Now the works of the flesh are plain: fornication, impurity, licentiousness, idolatry, sorcery, enmity, strife, jealousy, anger, selfishness, dissension, party spirit, envy, drunkenness, carousing, and the like. I warn you, as I warned you before, that those who do such things shall not inherit the kingdom of God. (Gal 5:19-21)
Note then the kindness and the severity of God: severity toward those who have fallen, but God's kindness to you, provided you continue in his kindness; otherwise you too will be cut off. (Rom 11:22)