What do you feed upon? Whatever you feed upon is eventually what you will become. It is very important what you put into your mind and heart.
Spiritual things are what pertains to your spirit. Spiritual things, for example, are things such as reading the Bible, praying every day, and acting according to what the Bible teaches. Fleshly things are what pertains to the flesh (what your sinful, carnal nature desires to do and feed upon) such as worldly movies, video games etc.
You should feed on spiritual things, not fleshly things, so your spirit man will be strong. For instance, if I put two dogs in a ring, which one is going to win? The one which you feed the most! If you put a skinny, malnutritioned dog in a fight and a well-fed dog in a fight, the one you feed the most is going to win. It is as simple as that and you want your spirit to always win out over your flesh!
If you feed on the Bible every single day without fail, you will think about and act according to what the Bible says. However, if you feed on worldly things constantly, you will act according to what you have taken in (Read James 4:4).
Remember, whatever you feed on, that is what you will most likely become. You choose what you feed on every day and no one else can make that choice for you. You need to fill up on the Bible and spiritual things. Do you read your Bible every day? Do you pray without ceasing as the Bible says in 1 Thessalonians 5:17? Do you witness on a regular basis, doing the work of an evangelist as we are all called to do (2 Timothy 4:5)? All these are a part of making your spirit man strong.
Fleshly things are, for the most part, doing things that are vain, empty, and worthless in the sight of God. Your life is a field and you are planting seeds in the soul of your heart on a daily basis. What do video games or stupid movies add to your life? Anything that does not add to your life for eternity is vain.
Again, always remember that it is a choice that is up to you as to whether the Spirit or the flesh wins in your life. I hope now you can make the distinction between the two. Remember, put spiritual seed into the field of your life. Do not allow fleshly seed to gain root in the soil of your heart.