The principle
Any momentary triumph you think you have gained through argument is really a Pyrrhic victory; the resentment lasts long after the words are forgotten.
The application
Convince by demonstration, not debate. A shipped result settles a dispute that a thousand arguments cannot. The corollary: when an argument is unwinnable on its merits, do not win it — outlast it.
The defensive tell — how to spot it being run on you
When someone keeps trying to drag you into a public debate about something you have already decided, they are not seeking truth — they are seeking your time and your visible attention. The reply is to ship, not to spar.