Well, not too much of it anyway.
I just decided one day that physical pain is pointless. It is designed to be a signal to inform you that your body is being damaged, which is a good thing, but I don't see a reason why the signal has to be so uncomfortable. So on that day that I tried to hack my own mind, and I found out that it was not behind a firewall.
Here's how I did it:
First of all, I had to establish a clear analogy for the situation. There was a system or a program, created by God or evolution or whatever you want to believe. I have this system or program and I need to change one little thing - just disable something that my own body does. How hard can this be?
Establishing this clearly in my mind was defiantly the first and most important step to my immunity.
Next part was easy, I just kept telling myself that I am in control over the situation and rationalizing the pain every time it comes. I accomplished this by describing the feeling in my head and what it is for. My thoughts were something along the lines of "Now I feel my fist hitting the wall. A signal is being sent to my brain from my hand indicating that a bunch of cells were killed. A good idea now would be to stop hitting the fist against the wall."
At this point the pain was gone. All that was left was the knowledge of the situation my body is in.