...just as it has been doing among you since the day you heard it and truly understood God's grace. Col. 1:6, NIV
The Gospel grew and bore fruit because of two things.
First, they heard about it. The seed was planted. How can someone respond to the Gospel without being told about it? We have to hear about it. Evangelism is not the only thing in the Christian life, but it is a vital part of it. We need to share the good news with those around us. The good news is that we can have a relationship with God as we were created to.
Second, they understood God's Grace. God's Grace is His choosing us, working with us and enabling us for His own good pleasure based on no work or attribute of our own. When we begin to realize that we are loved by God because of Who He is, not because of Who we are, we can let any tension in our relationship with God seep away. We can be at peace. We can work with confidence. We can be who we were created to be. The joy of the Lord can be our strength.