Too much of a good thing - examples of production (or utility) functions that are initially increase in a factor and then decrease
$$F(R,T)=100000-(R-200)^2-(T-25)^2,$$

where $F$ is production (in kg), $R$ is rainfall in a year (in mm), and $T$ is average temperature over the course of a year (in °C).

This says that under the optimal growing conditions of $R=200$ and $T=25$, production will be 100,000 kg.

If rainfall $R$ or temperature $T$ is higher or lower than these optimal levels, then production will be lower than 100,000 kg.

(Concepts you may be looking for include satiation and bliss point.)