Patriotism is like family love. You love your family just for being your family, not for being "the greatest family on earth" (whatever that might mean) or for being "better" than other families. You don't feel threatened when other people love their families the same way. On the contrary, you respect their love, and you take comfort in knowing they respect yours. You don't feel your family is enhanced by feuding with other families.
While patriotism is a form of affection, nationalism, it has often been said, is grounded in resentment and rivalry; it's often defined by its enemies and traitors, real or supposed. It is militant by nature, and its typical style is belligerent. Patriotism, by contrast, is peaceful until forced to fight.
The patriot differs from the nationalist in this respect too: he can laugh at his country, the way members of a family can laugh at each other's foibles. Affection takes for granted the imperfection of those it loves; the patriotic Irishman thinks Ireland is hilarious, whereas the Irish nationalist sees nothing to laugh about.
The nationalist has to prove his country is always right. He reduces his country to an idea, a perfect abstraction, rather than a mere home. He may even find the patriot's irreverent humor annoying.
Or, put another way, I would hold nationalists in the same esteem as Bill O'Reilly might hold "pinheads."