Paul crafted his "testimony" from his personal background.  It was tailored to particularly resonate with those who sought justification by their own self righteousness.

Each of us has come on a different journey.  And because of that, there is something in our lives that may particularly resonate with a hearer.  But the purpose of a testimony is not to tell how great we are, but to describe our journey to faith.

Too often, the modern testimony is nothing but a bragamony.  "And after my twelfth Super bowl ring, fifth world series ring, and after having one-night stands with over five thousand groupies, (including four international super-models, sixteen famous actresses, and one duchess), there was still an emptiness in my life.  I joined the army.  After receiving three bronze stars, two silver stars, the distinguished flyers cross, and becoming only the second person in history to earn the Congressional Medal of Honor twice, I was invited to the white house.  And after meeting privately with the president for several hours, and addressing his entire cabinet, I walked outside, and I realized there was an emptiness inside me.  I knew I needed God in my life."

The gospel is not about how great we are.  It is about our great God and Savior, Jesus Christ.  And our testimony is not how God became "yummy in our tummy."  Without question, the quest for meaning and purpose are powerful.  But not everyone achieves a sense of purpose simply because they come to faith in Christ.  Some go to their grave clinically depressed and emotionally unfulfilled in this lifetime.  But no one who has ever come to the cross has walked away dead in their sins.  They walk away alive in Christ.  The gospel is that Christ died for our sins, and rose again from the dead.  May this truly be "our testimony."