Write me every day about these points and anything else. When you have nothing to write, write and say so.

[De omnibus cotidie scribas. Ubi nihil erit quot scribas id ipsum scirbito.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher

Epistulae ad Atticum [Letters to Atticus], Book 4, Letter 8, sec. 4 (4.8.4) (55 BC) [tr. Winstedt (Loeb) (1912), 8a]
    (Source)

(Source (Latin)). Alternate translation:

Write me word on these points and all others every day. When there is nothing for you to write, write and say so.
[tr. Shuckburgh (1900), 8b]

Even if you have nothing to write, write and say so.
[ed. Harbottle (1906)