Did you ever notice that the best sermon illustrations are drawn out of the bad decisions we make. Maybe it is because there is so much to learn from them. The apostle Paul wrote that he couldn't understand why he did the things he didn't want to do. He noted that he knew what he was supposed to do and he did the opposite.
I've talked about that a lot in sermons and used my struggle with food, junk food, as an example. I grab that cookie, that bowl of ice cream, that hand full of chips even though I know I don't need them. I can't seem to help myself. When I do this I get a lot of people shaking their heads because they understand.
The truth is that we are all human. We are prey to the same kind of temptations and failings. So when we share the results of the bad decisions or wrong choices we have made, we are usually in good company.
The job of the preacher is to use the illustration and then help people figure out a way to make the right decision next time using the power of Christ to stand strong. In that way we can avoid the pitfalls of those bad decisions and bring glory to God.
Of course you don't have to be in the pulpit to do this. Every one of us can do that as we interact with the people we know. We can tell our stories and be conduits of God's grace and healing power with our friends, neighbors and co-workers.
After all, we are ambassadors for Christ. So don't let the fact that you aren't perfect stop you from sharing your testimony. It will only make it more real and believable to the person you are talking to and show the power of God's grace to heal and bring forgiveness.
So go to it.