Definition of "ABC" poker?

I have a specific reason for my opinion on bankrolls - and I have explained it here:

THE BRAIN AND POKER

Basically, it boils down to the fact that if you are playing at limits higher than what your bankroll can manage, it is extremely likely to affect your play because you will be overly attached to your immediate financial gains and losses.

You say "Show me a poker player who is rigid in their poker beliefs, and I'll show you a losing player." I say show me an undisciplined poker player and I will show you someone who will never be a winning poker player in the long term."