When you muscle through an additional hour of work at the end of an intense day, the marginal return of the additional hour is negative.

When you take on another project during a period of intense activity for the whole team, the marginal return of the additional project is negative.

When you push yourself way beyond your physical limit after two hours of intense workout, the marginal return of the additional effort is negative.

When you send just one more comment on top of a chat conversation that already features more than twenty other voices, the marginal return of the additional comment is negative.

When you read one more article on a topic you are ready to write a full thesis about, the marginal return of the additional article is negative.

The cost of not knowing when it is time to stop is diminishing returns that compound over time.

It is exhausting.