Timeboxing
Fixing a hard time limit on an activity and stopping when it expires, regardless of completion, used to keep open-ended work from consuming unbounded effort. A spike timeboxed to two days or a meeting timeboxed to thirty minutes forces prioritisation and surfaces whether the remaining work is actually worth more time before you've sunk it.
Timeboxing works because it inverts the usual question from "how long will this take?" to "what's the most valuable thing we can do in this fixed window?" It caps the downside of open-ended work, research spikes, meetings, investigations, that would otherwise expand to fill any space given. The discipline only pays off if the box is actually respected: a timebox you routinely blow through is just a soft deadline wearing a fancier name.