law of diminishing returns

the harder you try the less likely you'll be able to continue.

The tendency for a continuing application of effort or skill toward a particular project or goal to decline in effectiveness after a certain level of result has been achieved.

How the Law of Diminishing Returns Works with Communication
The more you talk, the less people listen. The more noise you make, the more it sounds like a drone. This is an economic principle, and it applies to communication, too. The paradox of attention is this: the more you try to get, the less attentive your audience becomes.