Scars
My first tattoo is the kanji symbol for scars. My reason for getting it was my diagnosis of Multiple Sclerosis. There is no Kanji symbol for MS, so scars seemed the most relevant. We all bare scars from wounds of all kinds. I felt it was appropriate to tattoo the skin of spinal cord to symbolize the scaring you cannot see.
Scars are the battle wounds we bare. Those scars we can see remind us of the time and hold the memory of when it happened. I feel these types of scars are easier to heal psychological speaking. The hidden ones, the ones we carry but have no physical evidence of them happening, are the ones we struggle to heal.