What's the quickest way to build stamina for a couch potato?

I was an athlete in high school, but like a lot of former school jocks that's where it ended. I just turned 33 last. I took up BJJ martial arts last November and competed in my only tournament in February. I took first in my division. To be fair there was only 4 competitors in total. Since then I have not been... show more I was an athlete in high school, but like a lot of former school jocks that's where it ended. I just turned 33 last. I took up BJJ martial arts last November and competed in my only tournament in February. I took first in my division. To be fair there was only 4 competitors in total. Since then I have not been able to afford to train, due to mortgage, kids, and everyday life. I see that there is a very big tournament coming up in less than a month, and I would really like to compete, but I'm afraid my cardio is shot again. I don't smoke but don't do much else other than work. What should I do to get my cardio in some kind of working shape in time?
Update: Cari you make some great points, and really hit the nail on the head with your assessment. I would like to hear or read more, but the links you have provided do not pull up on my computer. Do you have any alternative sites?
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