How does.the feeling of nationalism occur????

Nationalism is an ideology and movement that promotes the interests of a particular nation (as in a group of people)[1] especially with the aim of gaining and maintaining the nation's sovereignty (self-governance) over its homeland. Nationalism holds that each nation should govern itself, free from outside interference (self-determination), that a nation is a natural and ideal basis for a polity,[2] and that the nation is the only rightful source of political power (popular sovereignty).[1][3] It further aims to build and maintain a single national identity—based on shared social characteristics of culture, ethnicity, geographic location, language, politics (or the government), religion, traditions and belief in a shared singular history [4][5]—and to promote national unity or solidarity.[1] Nationalism, therefore, seeks to preserve and foster a nation's traditional cultures, and cultural revivals have been associated with nationalist movements.[6] It also encourages pride in national achievements, and is closely linked to patriotism.[7][page needed] Nationalism is often combined with other ideologies, such as conservatism (national conservatism) or socialism (socialist nationalism).[2]

By the the patriotic songs and poems.And by the flag