English Standard Version (ESV)
When someone is trying to sell me something, I want to know if they're using their own product. Do they believe in the product enough to use it? Does their live demonstrate the truth of what they say?
In Samaria, where Philip was preaching the Word, there were actions and signs that backed up his preaching. Unclean spirits were cast out, paralytics were healed -- there was evidence of the truth behind Philip's words.
When we proclaim the Gospel, do our lives demonstrate that we trust in God's Word? Do our actions demonstrate how we acknowledge Christ as Lord of all, of our time and our money and our work? We don't have to be perfect, but our lives should show that we are striving to serve Christ in word and deed. There should be evidence when people look behind the curtain to see if our life matches our words.
Inevitably, joy follows the Gospel. When the Gospel is changing lives, joy follows. The Holy Spirit transforms lives, and people see the freedom made possible in the Gospel -- and they are released from anxiety and worry, and into joy.