Your mind is amazing, far more powerful than the most sophisticated computer ever constructed. Your brain can quickly and constantly adjust to the ever-changing environment around and within you by making new synaptic connections and pathways. These new connections enable new thought processes to occur and enhance how you can approach novel problems.
To maintain such connections the mental pathways need to be used so that the connection is strengthened, otherwise it will be broken down and discarded to maintain the lean, mean thinking machine of your mind.
God has designed the Church to work a bit like this too. Jesus told us to always remain connected to him, the true vine from whom we draw our life. Stemming from this life He gives we connect with others and build them up, gaining new strength ourselves from the interconnected relationships.
Rather, speaking the truth in love, we are to grow up in every way into him who is the head, into Christ, from whom the whole body, joined and held together by every joint with which it is equipped, when each part is working properly, makes the body grow so that it builds itself up in love. (Ephesians 4:15-16 ESV)