Slowly, you get there.
Pound the pavement regularly enough and 5k becomes doable again. Hop on the bike day after day and the miles are no longer insurmountable. Swim enough mornings and even a land lubber like me begins to approach the needed distance.
Fifty-six days until the triathlon. I'm in a very different place than last year. Not as panicked, determined to better my time, and on my way.