When your work schedule begins to get crowded, there is a simple and obvious solution:
Throw stuff overboard.
Now if that's so obvious, why don't more people do that? I encounter individuals [that can include the person in my mirror] who run themselves ragged because they seek to do the optional along with the necessary. Low priorities are mixed in with the high and the stress level soars. That's why any "to do" list on a project should also include a "won't do" category.
There are few events more liberating than the conscious decision not to do something.