"Halfway from coal, halfway to diamond" is all about being in the middle of some kind of journey or transformation. The next line, "My fall knocked a mean chip out of me", indicates that the narrator has 'seen the light' in some way. Something happened that knocked them off of their pedestal. However, the process of going from 'jerk' to 'nice guy' (or whatever the transformation is) takes a long time, sort of like the amount of time it would take a lump of coal (with sufficient heat and pressure) to become a diamond...
"Halfway from coal, halfway to diamond" is all about being in the middle of some kind of journey or transformation. The next line, "My fall knocked a mean chip out of me", indicates that the narrator has 'seen the light' in some way. Something happened that knocked them off of their pedestal. However, the process of going from 'jerk' to 'nice guy' (or whatever the transformation is) takes a long time, sort of like the amount of time it would take a lump of coal (with sufficient heat and pressure) to become a diamond...
unless you're superman.