I'm not trying to minimize the battle we are in. I get the flesh issues from ample experience. And I get that a badly corrupted flesh can put up an extreme fight, leading our minds this way and that way, and sometimes in horrible ways.
It's in faith that we overcome. Paul wrote that he beat his body to keep it under. We need to do whatever harsh seeming thing we need to do to help ourselves in the fight against sin, but I still say, it is in our faith that we will find victory. I don't think Paul was talking about self-flagellation. And if not that, it's metaphorical, and I would think to speak towards the extremity in how we see the flesh, and our fight against it.
That fight has already been won for us be Christ. I would to God that we could each of us have a total trust in that in all times, because in that IS our life of victory, overcoming the flesh each time.
In Christ, by faith in Christ, we know only victory. But . . . be it to us according to our faith!
Much love!