The postmortem for Past Present goes into my thoughts around building it, so I won’t repeat that here.
The deadline of a comp (in my case, the Winter TADS Jam) was an important part of the process, and kept me focused on finishing the project. So, I would add to the above that comps and jams serve as a good way to keep one motivated.
I’ve said elsewhere the Past Present is my first computer game, and that the impetus for finishing it was to complete a lifelong goal of writing one. Recently I remembered I coded a Core War implementation many years ago for the Atari ST. It’s not interactive fiction, though, and I didn’t design the game’s rules, merely ported it to the platform. Still, in a technical sense, it was my first game. (And fun to write.)