Chiron

I love Chiron. Chiron is where our deepest wounding lies. What makes us suddenly well up in tears on a perfectly nice day. The place where if it is poked evokes such pain it can come out as anger.
He is given the name "The Wounded Healer", or called "the wound that never heals".
He symbolizes where we are healed and then in turn heal others.
The wound Chiron symbolizes in our natal charts is always but always something that happened in another lifetime or existence. It is the pain that you incarnated now to heal. Unfortunately that means that you re-experienced it in some way during your current lifetime. Most of the time it is something that occurred in childhood. 
The glyph of Chiron looks like a key. 

That, of course, is quite significant. Chiron revolves around the sun between Saturn, the lord of karma and Uranus, the breaker of chains/ freedom from our karma. Chiron takes us off of the karmic wheel once we go into that wound, share forgiveness for it and allow ourselves to be healed and set free.