Sorry I tried to add the alternate line on move 6. Kc3 but it's not there? But that also works. Anyway, just a simple tactic to keep in mind so you don't get flogged on the battlefield like I did!
King + pawn vs. King

And maintain the opposition. By moving 2.pKB4 you gave up the opposition.
I assume you meant the 3... c5, if that is the move you are talking about I still could have won if my next move would have been 4... Kc4 rather than pushing the pawn in front of my king. Aside from that you are correct in saying "maintain the opposition."
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Here is a blitz game I just played and ended up with a draw because I missed a simple endgame tactic that will kill you in blitz chess if you don't know it. Here is the end of our game