But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judea, and in Samaria, and unto the uttermost part of the earth.
Acts 1:8 (KJV)
The Holy Spirit is our power source, and we ought to draw on Him continually. He enables us to go into the world and be effective witnesses for Christ. When we follow the promptings of the Holy Spirit, He will show us what to do and what to say, and He will help us to live as examples and demonstrations of the love, grace and mercy we ourselves have received.