Even though “affection” is quite a good and strong rendering in the Book of Colossians 3:2 Set your affection on things above, not on things on the earth.
The Greek word, “phroneo” is more practical. It means to set your mind or your thoghts; how your mind works and originates from two words; which are “To reign in,” like you say, “I’ve got to reign this fellow in”; that is, to bring him under control while The second word means, “To block in or fence in.”
The admonition to set your affection on things means to have control on your mind & consciously set your thinking on spiritual things.
Remember that the things you think about are the things that will control your all your actions. E.g., you may have been dealing with certain habits that affect the way you serve & live for the Lord, the habits that reduce your effectiveness and efficiency.
You might have prayed about some things, yet nothing seemed to have changed. It is not so much about prayer as it is about the use of your mind! Your mind is a very powerful machine that you can twist or control it in any way you choose, what you must do is to first consciously refuse to think on those things you know are not wholesome and deliberately focus your mind on the Word
Always exercising your mind through conscious thought for whatever reason, if an unwholesome thought comes to you, say, “No,” and then, switch your mind to something best for you, to the Word. Don’t be surprised if such thoughts creep in again; resist it and repeat the process. James 4:7 says “…Resist the devil, and he will flee from you.”
Only God knows what is in the devil, and He tells us if we resist him, he would flee; that’s got to be the necessary result!