To grow in Christ you have to feed the spirit.
Food is essential for growth, physical food is used to nourish the body while spiritual food is for the spirit.
The word of God is a spiritual food, when you also Pray or worship God, you're nourishing the spirit.
The spirit gets sick when you don't feed it. The way to know that your spirit is a sick is when you start having evil imaginations and start considering sin to be bad.
FEED THE SPIRIT EVEN AS YOU NOURISH THE FLESH. STUDY THE WORD.