Snake venom
The spiritual man willingly confronts difficult situations. He makes himself vulnerable, to bring his weaknesses and their accompanying delusions to the surface where they can be recognised and dealt with. Thus does his suffering facilitate healing.
You can inject snake venom into your blood to gain immunity. There may well be fever at first, but one emerges the better for it. The weak cannot take large dosages, so their progress is slow. The strong transfer their blood for poison; they gain immunity rapidly.
It is sometimes better to make a small incision to diminish a worse pain.