"If one follows through consistently with the practice, over time, difficult emotions will subside"

Consistency is very hard to achieve, the same level of concentration, determination, effort, every day. Could just a small amount of hesitation or distraction make the difference?

I'm a really inconsistent person, so one day the illness that accompanies me everywhere is a tolerable shadow, the next it is a devastating storm. Yet, despite the inconsistency I'm still here and still managing the difficult emotions and not giving in to seriously harming myself.

Maybe the reference to difficult emotions subsiding is more about gaining a surer ability to manage the feelings, than having the emotions diminish or disappear altogether? You certainly have developed an infinite amount of patience, in that you seem to accept that this will be a lifelong wait.