When studying what an expert knows/does, the question is, "what are events that if happen are (at least temporarily) irreversable and that change the dynamics? "
In the game world, this might include your characterer, after losing health (a primary variable), finally dies (a trigger).
- In the real world, after working hard to improve productivity (a primary variable), you might get a promotion (a trigger).
- After working hard to figure out a solution with a perspective client (a primary variable), you might get the contract (a trigger).
- After building support for your bill (a primary variable), you might get a favorable vote (a trigger).
Triggers and primary variables go hand in hand. Talking about one without talking about the other misses the point.