Selections from Acts 2
Peter stood up with the Eleven, raised his voice, and proclaimed to them: ... "Let all the house of Israel know with certainty that God has made this Jesus, whom you crucified, both Lord and Messiah!" When they heard this, they were pierced to the heart and said to Peter and the rest of the apostles: "Brothers, what must we do?" "Repent," Peter said to them, "and be baptized, each of you, in the name of Jesus the Messiah for the forgiveness of your sins, and you will receive the gift of the Holy Spirit."... And with many other words he testified and strongly urged them, saying, "Be saved from this corrupt generation!"
You'd hardly believe this was the same fellow who couldn't even stand up for Christ to a young local girl around the campfire the night they sentenced his Master to death. Listen to him now, though - fearlessly firing off the hard facts. You haven't heard the last of this guy.
Charles Spurgeon said that few of us have an adequate idea of what we may become - even here on earth! - by God's divine power and grace. We know one day we'll stand around the throne, with every pore in our being seeking a way to widen our praise. But if we just knew what he could do through us even now - with our pride beaten to a pulp, our doubt driven out the back door, our fear banished to the outfield. We can do all things - everything! - through him who gives us strength. Or were we just dreaming that?
Look at it this way ...
When God purposes to do something through you, the assignment will have God-sized dimensions. This is because God wants to reveal himself to you and to those around you. If you can do the work in your own strength, people will not come to know God. However, if God works through you to do what only he can do, you and those around you will come to know him. Jesus said, "He who does the truth comes to the light, that his deeds may be clearly seen, that they have been done in God" (John 3:21, NKJV). When other people see you experiencing God, they are going to want to know how they, too, can experience God that way. Be prepared to point them to God. You will need to be very careful that any testimony about what God has done only gives glory to him. Pride may cause you to want to tell your experience because it makes you feel special. That will be a continuing tension. You must avoid any sense of pride. Therefore: "He who glories, let him glory in the Lord" (1 Corinthians 1:31, NKJV). - Henry Blackaby
A final thought:
If you're worried about the way your words will come out, or concerned about the impression you'll leave behind, give God a chance to take over. You won't have a thing to worry