Hi there, we overdo something when we spend much more time, energy and effort than is necessary in accomplishing a task. Often, the extra time, energy and effort we expend does not improve the quality of our work much more. Back to your example, reading is a good and productive activity, but do not read excessively and ignore other parts of your life. Hope this helps. Cheers, Lance

To "overdo" something means to do too much. Apples are healthy food, but if I were to eat twenty apples I would be overdoing it.

Overdo = to do something an excessive amount.