Ziri is digressing.

I'm sorry, I digress.

If you'll pardon my digression, I'd like to relate a little anecdote that will help me to prove my point.

After digressing, he returned to the subject.

My history teacher is awful: he begins talking of a topic, and then he starts digressing, and I think not even he realizes what he had explained.

The digression is escalating more and more.

But I digress.

You digress!