It’s nice when a design finally clicks. The pieces come together and it can start to handle the pressure of players pushing the game.
Last night I had two play tests of Plutocracy. In the second game one player kept completing missions. Completing a mission gives you a point and expands your abilities for the future. My thought was that players would complete a roughly equal number of missions each game.
While this player was grabbing up all the missions I was worried that it would break the game and I would have to find a way to fix it, again. But in the end he lost by 2 points. While this is only one instance and the game will need to continue being stress tested, it was nice that it managed to pull through without a runaway winner.
The reason it held together was that missions have diminishing returns. They are always worth 1 point but the extra actions you gain from them become less useful as you get more. And there are other parts of the game that will earn you more points than the missions as the game progresses.
You probably have an idea of how you want players to play your game, and if you have good incentives, players should generally follow your plan. But be aware of other things players could do and if those things would be a dominant strategy.