AMEN Dave in Tenn, AMEN!!!
To add to Mike's post.
In the Revelation passage, those who overcome are not pictured as "testifying" to others. Nor are they testifying (solely) about their personal faith. They overcome by the blood of the Lamb and by the word of their "testimony".
What is more important--your faith and/or the story of your faith, or the One in Whom you have faith...The One who died for you. Is the Gospel more important or is your faith in the Gospel more important?
If you picture a courtroom (and Paul was quite literally in "court" at the rough time of his revelation/vision) YOU are not the only one being "accused". (What he does to the least of these My brethren he has done to Me). You and me and every other believer are not all that important in the grand scheme of things. HE is paramount. When we "testify" of things in this court where Satan is accusing day and night, we are testifying not about our own experience but of the work, character, and promise of God. We are testifying the things concerning HIM.
The night my spiritual eyes were opened is important to me. Telling that story may be of encouragement to other believers. But I didn't die for their sins. And since that night, day and night constantly, the Adversary (in court) continues to "accuse". It's not enough for me to wrap myself up in the blanket of my own testimony. What is VITAL is that the Lord Himself be and remain TRUE. HE's the One whose Testimony frees the brethren--all of them. The ones in the revelation testify against the accuser on behalf of the Lord and His brothers.
Here's a spiritual match:
1Ti 4:9 Faithful is the saying and worthy of all welcome
1Ti 4:10 (for for this are we toiling and being reproached), that we rely on the living God, Who is the Saviour of all mankind,
1Ti 4:11 especially of believers. These things be charging and teaching.
That's OUR testimony (the especially) in this spiritual court on behalf of the brethren being accused day and night. If you can testify/provide witness/bring evidence to that, then you are among those who are overcoming.