We all have a story to tell about God's goodness and faithfulness made evident in our life, and God is most interested in using that story as a powerful witness that will bring salvation and motivation to other people.
Every one of us is called to be a witness for God. In a court of law, a witness is someone who testifies about "the truth and nothing but the truth" about an experience or a person. We are in the same way called to be witnesses about the truth about what God can do and what He does do by sharing our experiences with Him.
Being a witness for God is a great privilege. If done in the right light and in the right way, we will be a big blessing to the people around us. Revelation 12:11 says, "And they have conquered him by the blood of the Lamb and by the word of their testimony, for they loved not their lives even unto death."
But just as it can be done right, it's also possible that a testimony can be given in the wrong way. One common way that we Christians can do that is if it becomes too much about our faithfulness than about God's faithfulness. There are generally three parts to every testimony: your life before you met Christ, the point where you decide to give your 100 percent to Christ, and the life you now live in Christ. Every point of our testimony zeroes back to the true hero of your story: Jesus Christ.
The most powerful thing about our testimony is that most of it has nothing to do with our good works and our abilities. If it were then a testimony wouldn't be as miraculous and powerful as it should be. Our testimonies should be riddled with nothing less than the intervention and invasion of God's grace through Jesus Christ.
Looking back at the things that you have experienced, without a shadow of a doubt we can say that everything that was ever good came through God's goodness and not ours. James 1:16-17 gives us this warning to avoid us from getting led astray: "Do not be deceived, my beloved brothers. Every good gift and every perfect gift is from above, coming down from the Father of lights with whom there is no variation or shadow due to change."
Again, there is undeniably every reason to believe that the heroes of our stories are not us. God comes to save the day even when we are faithless, down, and hopeless. That's how God works, and that's how our testimonies should be. The story of God's goodness in our life has very little to do with what we do. It has more to do with what God has done. That's what gives power to a testimony to impact the lives of others around us.
