The person paying for careful work deserves time that has not been sold twice.

Attention cannot be split without cost, though it can easily be billed twice. Work done while half-committed elsewhere, an hour also serving another client, a promise made to more people than the calendar can hold produces a version of the job that looks complete and is not. The buyer usually cannot see the difference until much later.

Look at where you have promised the same hours in two directions. Fix the calendar rather than the appearance of it. If you are overcommitted, say so now, because everyone involved would rather hear it early.