How serious is the battle? Well, the verses speak for themselves. In fact, Jesus taught the ideal is to for the extreme.
Luke 9:57-62
57 As they were walking along the road, a man said to him, “I will follow you wherever you go.”
58 Jesus replied, “Foxes have dens and birds have nests, but the Son of Man has no place to lay his head.”
59 He said to another man, “Follow me.”
But he replied, “Lord, first let me go and bury my father.”
60 Jesus said to him, “Let the dead bury their own dead, but you go and proclaim the kingdom of God.”
61 Still another said, “I will follow you, Lord; but first let me go back and say goodbye to my family.”
62 Jesus replied, “No one who puts a hand to the plow and looks back is fit for service in the kingdom of God.”
Luke 14:25-35
25 And there went great multitudes with him: and he turned, and said unto them,
26 If any man come to me, and hate not his father, and mother, and wife, and children, and brethren, and sisters, yea, and his own life also, he cannot be my disciple.
27 And whosoever doth not bear his cross, and come after me, cannot be my disciple.
28 For which of you, intending to build a tower, sitteth not down first, and counteth the cost, whether he have sufficient to finish it?
29 Lest haply, after he hath laid the foundation, and is not able to finish it, all that behold it begin to mock him,
30 Saying, This man began to build, and was not able to finish.
31 Or what king, going to make war against another king, sitteth not down first, and consulteth whether he be able with ten thousand to meet him that cometh against him with twenty thousand?
32 Or else, while the other is yet a great way off, he sendeth an ambassage, and desireth conditions of peace.
33 So likewise, whosoever he be of you that forsaketh not all that he hath, he cannot be my disciple.
34 Salt is good: but if the salt have lost his savour, wherewith shall it be seasoned?
35 It is neither fit for the land, nor yet for the dunghill; but men cast it out. He that hath ears to hear, let him hear.