Instead of explanation, we cite an excerpt from the book by Yvo Kühling "Serbia Bites - reflections of proud country" (short stories about Serbia - local customs, everyday life and lifestyle of Serbian people, seen from the perspective of a foreigner):
The early autumn is the most pleasant time of the year in Serbia. While the heat of July and August hes faded, the fierce winter is still months away. Perfect circumstance for wining and dining, spoiling ourselves with the joy of spending time purposelessly. There is the Serbian expression that celebrates the joy of doing nothing, this specific Balkan flavor of hanging around all day, drinking coffees and rakija* at your local kafana** or café. I ask Marko at my favourite Senjak terrace about the nature of this proverbial wisdom: "Do you know this expression?" Marko: Nor sure if I understand, we Serbs have dozens of expressions for doing nothing".
So, if you like to experience the BLEJA, find your favorite cafe's terrace, order coffee and brandy, and do nothing!
*Rakija /ˈrəˈ'ki:ːə/ is the collective term for fruit brandy
**Kafana /kafǎna/ - a distinct type of local bistro which primarily serves alcoholic beverages and coffee, and light snacks ("Meze") and other food.