Paul does not pretend the body holds. Our outer self is wasting away. He states it plainly, which is more than most encouragement manages.
You notice it on the stairs, or in a photograph, or in how long it now takes to recover from an ordinary week. The bathroom mirror at six in the morning is not lying. Something is running down, and positive thinking has not changed the numbers on the blood test.
Then he puts a second process alongside it. Yet our inner self is being renewed day by day. Both are true simultaneously, running in opposite directions, in the same person. Day by day is the pace of it. Not one dramatic recovery, but something quiet and daily, like the decline itself, only going the other way.
That is worth sitting with if you are aging, ill, or simply tired in a way rest is not touching. Nothing in this passage asks you to reinterpret the decline as secretly fine. It asks you to believe something else is also happening that you cannot see.
Light and momentary, he calls the affliction, which is an extraordinary thing to write from a life like his. Later in the same letter he gives an account of beatings, shipwreck and prison. This is not a man who has had it easy. It is a statement about scale, not about severity. He is measuring against a weight of glory, and against that, almost anything is momentary.
We fix our eyes on what is unseen. Fix takes effort. Nothing about it is automatic.
So do it on purpose. Before you check the mirror or the results tomorrow, spend two minutes looking at the other ledger. What has been renewed in you this week that no scan would show. Write down one thing, and keep the list.