Luke 9:23 

“Whoever wants to be my disciple must deny themselves and take up their cross daily and follow me.”  The mark of a disciple of Christ, or in other words, a Christian, is self-denial.  This is the main trait that distinguishes you from a person who does not know Jesus.  This is what Jesus means by “Whoever wants to be my disciple must deny themselves.”  Without this characteristic, you are no different from a non-Christian.  In order to better understand the meaning of “deny themselves,” Jesus uses a scenario that people in the ancient Roman world would sometimes see: when they see someone carrying the horizontal piece of a cross (Latin, patibulum), they know that this person has been sentenced to death.  Thus, the call to deny oneself means to put aside your self interest for the sake of Jesus (see Luke 9:24).  Such an attitude is not something we do for only certain matters but is to characterise our entire life in every aspect.  This includes the way we use our time and money, how we relate to people, the goals we have for our children, the recreation we choose, etc.  As Christians, we must learn to live peaceably with everyone, even if we have to suffer loses.  That said, however, anything or anyone who competes for our love at the expense of pleasing or loving God must be given up.  In other words, God takes priority over anyone or anything.  This is called self-denial.  And the Lord will reward you for self-denial: “whoever loses their life for me will save it” (Luke 9:24). 

1 John 2:15-16 

“Do not love the world or anything in the world.  If anyone loves the world, love for the Father is not in them.  For everything in the world, the lust of the flesh, the lust of the eyes, and the pride of life, comes not from the Father but from the world.”  The word “world” does not refer to human beings who live in the world or to material things.  It refers to anything that opposes God.  There is nothing wrong with buying a nice car.  But if in order to buy that car, you do things that displease God, that thing is “the world.”  Verse 16 gives its details.  First, the “lust of the flesh.”  “Flesh” does not refer simply to the physical body.  Rather, it refers to the entire human being that is opposed to God.  “Lust” or “desire” is neutral.  Human beings have desires.  There is nothing wrong with desiring to eat good food.  Sexual desires are legitimate when they operate within marriage.  “The lust [or desire] of the flesh” refers to what a human being desires that oppose God.  Second, “the lust [or desire] of the eyes” refers to the desire that is produced because of what the eyes see.  Again, there is nothing wrong with such desires.  They are wrong, however, when the desires or what you do to fulfil the desires are sinful and displease God.  Third. “the pride of life” are things that will cause you to exalt yourself for the sake of wanting to feel good about yourself, or so that you can boast about it over others.  It is self exaltation. 

First John 2:15-16 commands us not to love such things in the world.  Such things may be neutral morally.  When, however, they cause you to do things that displease God, such things belong to the realm of the “world.”  If you love the world in this way, you do not love God.  Love God, not the world.