Mental Food
Heart keeping
23. Keep thy heart with all diligence; for out of it are the issues of life.
What does it means to keep our hearts? In biblical terms, the "heart" often refers to the inner person, including thoughts and emotions.
Guard your mind / thoughts
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.
God calls us for renewal of our mind. We have to align our mind with God's, in order to know the will of God.
8. Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things.
2. Set your affection on things above, not on things on the earth.
phroneō
fron-eh'-o
From G5424 to exercise the mind, that is, entertain or have a sentiment or opinion; by implication to be (mentally) disposed(more or less earnestly in a certain direction); intensively to interest oneself in (with concern or obedience): - set the affection on, (be) care (-ful), (be like-, + be of one, + be of the same, + let this) mind (-ed, regard, savour, think.
5. Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;
This verse calls for a proactive effort in controlling our thoughts, casting down our imaginations, everything that is not in accordance to the knowledge of God.
7. For as he thinketh in his heart, so is he: Eat and drink, saith he to thee; but his heart is not with thee.
Our character is defined by our thoughts.
22. That ye put off concerning the former conversation the old man, which is corrupt according to the deceitful lusts;
23. And be renewed in the spirit of your mind;
24. And that ye put on the new man, which after God is created in righteousness and true holiness.
The conversion happens in renewing of our mind. Our values get changed. See Titus 3:5, Colossians 3:10, Jeremiah 31:33.
3. Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.
Our mind has to be focused on God
Guard your eyes
3. I will set no wicked thing before mine eyes: I hate the work of them that turn aside; it shall not cleave to me.
Think about how does this verse applies to the things you see online, or any type of media?
22. The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light.
23. But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great is that darkness!
If the eye be evil, the whole body is full of darkness. If the light that is in thee be darkness, how great is that darkness? Even those things which are good, seems to be bad, because of my evil eye, how great of a darkness are the real things
Guard our tongue
14. Let the words of my mouth, and the meditation of my heart, be acceptable in thy sight, O LORD, my strength, and my redeemer.
God sees the content of our thoughts. And our thoughts will produce our speech.