Resign a Rook Down? Then how can I mate you?

After an unexpected but certainly not lethal move 11 I lost my mind and blundered a rook.  Then I was able to catch myself and set up a successful mating attack.  Of course my perpetual block on concrete calculation came into a play and I could only clearly see the draw OTB.  The lessons here:

Don't give up

Don't panic

Concentrate and Calculate