"Thou hast been faithful" is the highest possible commendation.
It may not be amiss to look a little at the meaning of the word as a standard of moral requirement.

In general, it implies the doing of all our work as well as we can.

All our work includes, of course, our business, our trade, our household duties, all our daily task-work, as well as our praying, our Bible-reading, and our obeying of the moral law.

We must not make the mistake of thinking that there is no religion in the way we do the common work of our trade or of our household, or our work on the farm, or in the mill or store.

The faithfulness Christ requires and commends takes in all these things.
Ofttimes, too, it would be easier to be faithful in some great trial, requiring sublimity of courage, than in the little unpicturesque duties of an ordinary day.