Start at the Outpost
The official store describes a loop of descending into shifting ruins, scavenging loot and furniture, surviving the Corrupted, and returning to rebuild the Outpost. The return is what converts danger into progress.
Before leaving, name the run: learning a layer, recovering useful furniture, seeking Grinder value, or supporting a team objective. A run with no purpose usually becomes an argument for one more room.

Carry a loss you can accept
The developer FAQ warns that a team failure can cost loot that was not extracted. Do not stake the Outpost's next upgrade on an unfamiliar descent.
Bring enough to complete the chosen objective, then preserve room for recovered value. A full inventory before the first meaningful find is a planning failure.
Leave on a decision, not a panic
Choose the extraction condition before danger forces it: a priority item recovered, a damage threshold reached, resources depleted, or the team losing coordination.
When that condition occurs, begin the return. The procedural layout means memorizing a perfect fixed route is less useful than maintaining orientation and retreat capacity.

Sources
Official GRAIN ROT Steam store page →
Developer-posted GRAIN ROT FAQ →