Good, bad, or just plain ugly...
Have you ever stopped and asked yourself; "What kind of witness am I for Jesus? Good? Bad? Or just plain ugly?" No matter how you answer the question you are at least acknowledging that you are a witness. Because of your belief in Christ, you are a tool of evangelism a tool that Jesus can and will use.
"But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth." (Acts 1: 8)
The tempter does a great job of convincing us that we can not be a witness. We have convinced ourselves that we don't have a enough biblical knowledge, we are not very theological, or we can't name all of the minor prophets. We are convinced that we are not a "witness" worthy of sharing the story of Christ.
Remember the blind man said "I don't know"
"Whether he (Jesus) is a sinner or not, I don't know. One thing I do know. I was blind but now I see." (John 9: 25).
Even with his self-proclaimed lack of knowledge God used him as a part of the Gospel Message of Redemption. For the blind man that was the extent of his testimony, because it was the extent of his experience with Jesus and it was used. At that moment he became a witness, why can't you?
Many Christians have never taken the time to think through the testimony of their experience with Christ. Yours could probably be explained in a few statements. Given the chance, those few statements might evolve into a more detailed presentation.
Mercer, Tom. 8 to 15, The World Is Smaller Than You Think (Kindle Locations 1958-1960). Oikos Books. Kindle Edition.