George Bernard Shaw, a much undervalued writer, has an interesting take on nationalism in his notes to John Bull's Other Island:
THE CURSE OF NATIONALISM’: ‘It is hardly possible for an Englishman to understand all that this implies. A conquered nation is like a man with cancer, he can think of nothing else,..... . A healthy nation is as unconscious of its nationality as a healthy man is of his bones. But if you break a nation’s nationality it will think of nothing else but getting it set again. It will listen to no reformer, to no philosopher, to no preacher, until the demand of the Nationalist is granted. It will attend to no business, however vital, except the business of unification and liberation.
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There is indeed no greater curse to a nation than a nationalist movement, which is only the agonising symptom of a suppressed natural function. Conquered nations lose their place in the world’s march because they can do nothing but strive to get rid of their nationalist movements by recovering their national liberty.
From this point of view, nationalism's true aim should be precisely to put itself out of business, i.e., to attain a state wherein nationality ceases to be a preoccupation, just in the same way as an ill man wants to be healthy so as to stop having to think about his body and get on with his life. It is the aim of nationalism to forget itself, just as the aim of health is to forget the body. Of course, there are nationalisms that don't quite see it this way. These other nationalisms are like an ill man who says 'Oh, to be healthy, so that I can celebrate and rejoice in my body, have rituals and festivals in its honour' etc. But only from the point of view of the invalid does the body appear this way; and similarly, the vision of the nation outlined by many nationalists is only an optical illusion created by their 'invalidity' (being conquered).
This perhaps relates to a more general point about radical politics: that its ultimate aim is to make itself disappear. Thus, the left are typically accused of being preoccupied with class and exploitation and so on. But their aim is precisely to be in a position to forget these things and start really leading productive lives - again, like the invalid forgetting his body. Nationalism, of the kind Shaw speaks of, and other radical movements are thus like symptoms, to be cured not through trained introspection but through revolutionary action.