"The sin of worldliness is the tendency to set one's affections on things of the earth rather than on heavenly things (cf. Colossians 3:2)." 
Romans 12:2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.
1John 2:15-16 Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him.For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world.
James 4:4 Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God.
2Peter 1:4 Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust.
Colossians 3:2 Set your affection on things above, not on things on the earth.
Romans 8:12-13 Therefore, brethren, we are debtors, not to the flesh, to live after the flesh.For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live.
Mark 8:34-36 And when he had called the people unto him with his disciples also, he said unto them, Whosoever will come after me, let him deny himself, and take up his cross, and follow me.For whosoever will save his life shall lose it; but whosoever shall lose his life for my sake and the gospel's, the same shall save it.For what shall it profit a man, if he shall gain the whole world, and lose his own soul?
- What is worldliness, and when is it sinful?, by Phil Johnson