I wonder what the ideal language course would be like. One of the things I'd certainly like to see is a course built around lots of little poems of the highest quality (or the most inspiring verses from longer poems). It would be easy to find the motivation to memorise them, and they'd be full of useful phrases which you can adapt to your own uses. I read through a Serbo-Croat language course many years ago, but most of what I learned has faded now because I could find nothing to read to maintain it afterwards. The part that stuck really strongly though was the poem it included near the start, and I've never forgotten it:-

Mala kuc´a kamena,
Sa tri mala prozora,
Zeleni im kapci,
I krov sav od plamena,
A na krovu vrapci.

Little house of stone,
With three little windows.
Green are their shutters,
And the roof is aflame,
But on the roof (there are) sparrows.

I can think of no better way to learn vocabulary and grammar than that. If you happen upon anything as beautiful as this poem in any language you've been learning, please share it here.