"If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God. Set your affection on things above, not on things on the earth."

                                 - Colossians 3:1, 2

We are born with a sinful nature. Nobody has to teach us how to lie, cheat, hate, etc. Those things come naturally to us. Likewise, our affections are naturally for the things of  the Earth. We don't have to make any effort whatsoever to be carnally minded, but it does require effort to be spiritually minded. That is why Paul admonishes us in this passage of Scripture to set our affections on things above.

"My son, if thou wilt receive my words, and hide my commandments with thee;
So that thou incline thine ear unto wisdom, and apply thine heart to understanding;
Yea, if thou criest after knowledge, and liftest up thy voice for understanding;
If thou seekest her as silver, and searchest for her as for hid treasures;
Then shalt thou understand the fear of the LORD, and find the knowledge of God."

                                 -Proverbs 2:1-5

Notice how many verbs are used in these verses: receive, hide, incline, apply, seekest, searchest, find, etc. Being spiritually minded requires a lot of effort,  but that effort is anything but wasted

"....to be spiritually minded is life and peace."

-Romans 8:6

Even though it requires a great deal of work to become spiritually minded, it only makes sense that we should be so. After all, our lives are but a vapor. How much more then are the things of this life! Why would we spend our time working for a treasure that will one day vanish away?

"For we brought nothing into this world, and it is certain we can carry nothing out."

                    -Timothy 6:7

If we spend our life being carnally minded, we are in essence building our castles in the sand, for material possessions and earthly achievements are only temporary. One day the "...earth...and the works that are therein shall be burned up." (II Peter 3:10) Any castles that we have built in the sand will then be destroyed. We will have to give account for the way we have lived our life and what we have made our treasure.

"For where your treasure is, there will your heart be also."

                    -Luke 12:34

If our treasure is on the earth, then we are carnally minded. But, if our treasure is in heaven, we are spiritually minded. We ought to strive to remain spiritually minded, remembering that, "...the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be." (Romans 8:7).