Everyone else had left, and Eustice was alone.
If you're a writer, do you ever have sentences like the one above? Do you ever conclude a paragraph restating what the rest of the paragraph has already established? Why do we do that?
There are at least three possible answers. The first is that we tend to build paragraphs like ladders, using the previous sentence as a step to the next. If we're not careful, this results in a lot of overlap. This can be fixed by close editing.
A second reason, really chilling, is we just don't have anything new to say. Once Eustice is alone, we don't know what to do with him, so we just keep emphasizing the one thing we can say about him. This is a good time to get another cup of coffee or go for a walk while you meditate on your next step.
A more serious problem could be that we ourselves weren't convinced the first time we wrote something. Not that Eustice's being alone is improbable but saying that, and only that, seems unsubstantial, so we say it again.
Everyone had left, and Eustice was alone. By himself. On his lonesome. Solo. No one in the place but him. Ay-el-oh-en-ee. Alone.
Have you ever read anything like that? Hell, I've written stuff like that.
The desire to repeat what you've already said is a sure sign you need to find a better way to say it in the first place, and the way to say it better is good old description. Imagine Eustice's environs as vividly as you can and isolate the details that detail his isolation. If you do it really well, you can convey his solitude without ever using the word "alone" at all.
Eustice idly ran his finger around the rim of his wineglass and thought about what he'd just said. He'd been right, hadn't he? Maybe he could have found a way to be more polite, but better to come out with it and get it over with. The people at the next table were pointedly not looking at him. This was a nice restaurant and customers respected one another's privacy, which is one of the reasons Eustice chose it. The half-finished glass of chardonay in front of him wore the mark of Margot's lipstick, but when he tried to catch the lingering trace of her perfume, it was already gone.
I think that works better. I had to cheat a little bit, adding some people at the next table, but it's a lot harder being alone if you don't have someone around to see you do it. Of course this way is a lot more work than just saying Eustice is alone and repeating it until you feel satisfied, but no one ever said writing wouldn't be work. Because it is. Work. Labor. Strain. Double-you - Oh - Ar - Kay. Work.