Near-miraculous
Imagine a computer that could repair itself. A key on the keyboard gets damaged, it fixes itself. The monitor gets a scratch, it fixes itself. Someone spills coffee on it, it cleans itself up.
Now imagine that this computer's software also repairs itself. A sector on disk containing part of your word processor or your term paper gets damaged, and the computer reconstructs the missing bits using other parts of the disk and bits of other software and data.
The human body and brain are really remarkable. I cut my finger, fairly deeply, a week ago, and though it's not totally healed yet (and looks to me like there'll always be a scar there), it's mostly healed. And I didn't have to do anything except keep it clean and (for a while) covered. It just fixed itself.
I hope to never have to test the self-restorative properties of the human brain myself, but they've been well-documented elsewhere—people being able to continue to function perfectly well with large portions of their brains destroyed by an accident, for example.
I find it really impressive that such a complex system as a body can repair itself. On the rare occasions when I don't just take it for granted, anyway.