I thank Dr. Gottfried for his response, and I appreciate the point that he and several commenters have made.  From the reaction to the last post, I see that I must not have been sufficiently clear about what I meant.  National consciousness did exist prior to the rise of nation-states, and indeed was the basis for the cultivation of nationalist feeling and the inspiration for conceiving of political organization along national lines, but that is absolutely not what I was talking about.  National consciousness in the Balkans is a complex matter, since most people until at least the 18th century still primarily identified themselves by their religion and among some nationalities (e.g., Romanians and Bulgarians) the educated members of these groups identified culturally as Hellenes up into the 19th century, but there were certainly stirrings of it in early modernity.  When Western-educated Greek nationalists began to organize the independent Kingdom of Greece, their idea of what Hellenism entailed clashed with the customs of the broad mass of the population, and the Greek nation imagined by the classically trained nationalists and the Philhellenes was one that had no necessary or obvious connection to the existing Greek laos.  One of the predicaments for Greek folklorists in the latter half of the 19th century was to reconcile the existing laos to the image of the ethnos.  National consciousness emerged sooner in those unified absolutist dynastic states that were able to exercise more control over different regions, and it emerged more slowly in places where there was a profusion of polities.  In western Europe even a distinctly national identity was a product of a particular region or principality, and the language that came to be treated as the proper national literary language was the one associated with the region or principality that took the lead in cultivating national consciousness into a more or less coherent political and cultural program.  

It is this program and the attachment to it that I am describing when I refer to nationalist feeling, which I would maintain is not the same as national feeling.  In the case of the latter, you could self-identify as part of a nation, a particular people, and yet that might take second or third or fourth place to other, more immediate loyalties, and it might not imply any political objective or aspirations for independence or sovereignty.  Nationalism is an ideology that tells someone who possesses a consciousness of being part of a certain nationality that this consciousness implies or requires the pursuit of a set of political goals; the move from having national feelings to having nationalist feelings is the move from self-identification with a national group to believing that this identity now takes precedence over most or all other loyalties and that it compels some kind of political action.  Nationalism inspires people to give priority to national identity and a political project undertaken in the name of the nation, such that national identity comes to trump religion or civic loyalty, and indeed revolutionary liberal nationalism required turning against the rule of foreign dynasties.  Multinational empires had existed for centuries with subjects who possessed national consciousness without meaningful disturbances; they began to fragment and suffer internal upheaval when those national feelings were given an ideological cast (i.e., when these people became nationalists).  To identify with an ethnicity means at a minimum that you believe that you are descended from common ancestors (whether or not you are) and originated from the same home country; in practice, the use of a common language is normally taken as evidence of shared ethnicity (even though the boundaries of an ethnicity need not, and sometimes do not, match up with linguistic lines).  Identifying with a nation of millions does require abstraction in order to imagine a unitary people spread out over hundreds of miles of territory, and it requires fashioning some kind of ideal type of who belongs to the nation to which the inhabitants of different regions in all their variety will then try to adhere themselves.  In practice, national unification and the pursuit of uniformity throughout the nation-state have come at the expense of whole regions that do not fit the mold crafted by those leading the charge for unification.  In this way, devotion to the Nation can directly conflict with the welfare of the people.  Likewise, the pursuit of national missions can have terrible consequences for the actual members of the nation, as the catastrophic failure of the Megali Idea reminds us.  The nationalist will treat such calamitous disasters as evidence of betrayal from within or by foreign powers or both, while the non-nationalist will tend not to embark on them in the first place. 

In my earlier post, I was not discussing how earlier national consciousness is directed by nation-building monarchs or politicians, but was considering how nationalists make use of patriotic loyalties to build up the nation-state.  These are not entirely unrelated processes, but they are different ones, and it was solely the latter that I was concerned with in the previous post.  I hope this has managed to remove any confusion that may have been created earlier.