Remember what the disciples said to Jesus in John 6:28? "What may we do, that we may work the works of God"? Jesus replied, "The work of God is that you believe into Him whom God has sent."
I posit that our first, and even unique, work as Christians is to repent and remember our Father in heaven, and return again to Him through our obedience to the faith in (and of) Jesus Christ.
Jesus, as you've written, is the unique Overcomer. He is the One who said, "I have overcome the world". We did not overcome; rather we were overcome (by sin, the flesh, the devil and the world) and we fell and were cut off from the Father. Jesus did not sin, yet He who knew no sin was made sin on our behalf (2 Cor 5:21). So Jesus' overcoming was to 1) not sin, and 2) become a sinless propitiation on our behalf. Our overcoming is to "see Jesus" and repent, and come back to the Father through faith in Him.
My point in writing is this: what of the "Christian" who "falls from the height", a la Rev 2:5? My exemplar in this regard is none other than St. Peter, who didn't "fall" more than you or I but rather whose failures are so well documented in the text. In the apostle Peter I see the Father presenting a model of the "normal" christian experience of failure, repentance and return. Again and again, "seventy times seven" as Jesus counseled him. It is the ones who seem to act as though they were somehow beyond failure (
MOTA, anyone?) that are probably in most peril. It seems as though they think the word 'repent' doesn't apply to them.
To reiterate: I see an overcomer as one who:
1) Fails,
2) Remembers the height from which he/she has fallen,
3) Repents,
4) And comes back (returns) to the first works.
http://en.wikipedia.org/wiki/Jesus_Prayer
I contend that we never 'graduate', in this present age from the position of 'mercy'. We just keep going. Some may think they are now immune: "Hold fast to your crown", as in Revelation 3:11. But that may be the minority position: 1 out of the 7 epistles says to hold fast, compared to 5 out of 7 urging repentance. So I still think it safe to be somewhat pessimistic in my position.
The good news is this: Once we have turned, and come back, we are able to help those who likewise suffer and go astray.
Luke 22:31 Jesus says (to Peter) "And when you have turned back, strengthen your brothers."
Likewise, Psalm 51, the famous "psalm of failure and repentance", says
12 Restore to me the joy of your salvation
and grant me a willing spirit, to sustain me.
13 Then I will teach transgressors your ways,
so that sinners will turn back to you.
How about that? David the overcomer!