Peter, John and Paul team-up to teach believers about the unfriendly life we enter from day one. John mentions the world (1 Jn. 2:16), Paul documents the flesh (Gal. 5:19-21), while Peter and John call-out the devil (1 Peter 5:8; Jn. 10:10). These are not only stumbling blocks in our lives but enemies of our souls.
According to 1 John 2:16, The World consists of the lust of the flesh, lust of the eyes and pride of life. Notice that John stresses "the lust of..." in the first two worldly enemies. This is the spirit of lust in the kingdom of darkness. It has responsibility over influencing our flesh - sinful desires that do not line-up with God's will for our lives and our eyes that deal with covetousness - something or someone we see and desire but should not seek for whatever reason. The pride of life will always maintain you can do whatever without any assistance from others, especially God's help.
According to Galatians 5:19-21, God provides a working list of what is considered The Flesh or detestable desires - "sexual immorality, impurity, debauchery, idolatry, witchcraft, hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions, envy, drunkenness, orgies and the like." These are straight forward, so I will not take the time to break them down. If you need further explanation, consult a dictionary.
1 Peter 5:8 speaks to an actual enemy and his nature - "Be alert and of sober mind. Your enemy the devil prowls around like a roaring lion looking for someone to devour." In John 10:10 Jesus gives the enemy a title of "thief" and describes his modes of operation - "The thief comes only to steal, kill and destroy;". But Jesus follows up this verse with what He came to do - "I have come that they may have life and have it to the full."
In fact, for The World, John records Jesus encouraging all who believe in Him that He has "overcome the world" - “I have told you these things, so that in me you may have peace. In this world you will have trouble. But take heart! I have overcome the world.” (Jn. 16:33)
For all our fleshly/non-Godly desires, Jesus Christ has paid the ultimate price - His life-blood. "For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. For God did not send his Son into the world to condemn the world, but to save the world through him." (Jn. 3:16-17)"For what the law was powerless to do because it was weakened by the flesh, God did by sending his own Son in the likeness of sinful flesh to be a sin offering. And so he condemned sin in the flesh," (Romans 8:3)