Spiritual warfare: Those who belong to Christ Jesus have crucified the flesh with its passions and desires
The apostle Paul describes for us the nature of spiritual warfare in his epistle to the Galatians: "For the flesh desires what is contrary to the Spirit, and the Spirit what is contrary to the flesh. They are in conflict with each other, so that you are not to do whatever you want" Galatians 5:17.
The spirit and the flesh are inclinations of the human being, we cannot always be good; and pretending that with mercy (compassion, kindness, gentleness) we fix all problems is utopian, selfishness, no matter how spiritually perfect we are at some point wins, and that is where sin appears, or to say, the flesh. He who pretends to be a saint at all times is because he shows a mask, we are all sinners and we are subject to error, no matter how much wisdom and understanding we have. But it is also true that in some people sin is something that comes naturally from the heart, while in others sin is the product of man's own weaknesses and not of his heart.
That is why in spiritual warfare we must take care of the poverty of spirit, that poverty that becomes humility before the Lord, and not go around criticizing the defects of others: "How can you way to your brother, ´Let me take the speck out of your eye,´ when all the time there is a plank in your own eye? You hypocrite, first take the plank out of your own eye, and then you will see clearly to remove the speck from your brother's eye" Matthew 7:3-5.
Belonging to Jesus consists in resolutely rejecting the inclinations of the flesh, sin should not be a habit but the exception: "Those who belong to Christ Jesus have crucified the flesh with its passions and desires. Since we live by the Spirit, let us keep in step with the Spirit" Galatians 5:24-25.
In the spiritual warfare Jesus constantly points the way to spiritual enlightenment and immortality: "Blessed rather are those who hear the word of God and obey it" Luke 11:28. If we live following the inclinations of the flesh, we will never attain the blessings of the spirit, Paul tells us.