In this case? Dama'ing when I drew the tile I needed for tenpai (a third 2s to net me a better pair, discarding 3p for a pinfu wait) as it was only two full turns until the end of the round and match, but then calling riichi after drawing and discarding the 7p, setting up a weak suji trap which my opponent immediately fell into.
Dora tiles are all luck, but that luck plus the smart play let me tie for first place, thus giving me the first place win.