Schumann's Kinderszenen are much on my mind as I prepare to play this cycle. It reminds me of the Dichterliebe cycle in its intense lyricism.
How would I define lyricism? A distillation of every element of a work such that no instant, however fleeting or seemingly ordinary, is without meaning. In other words, a relishing of the moment.
This might do as a definition of the opposite of sentimentality: a swimming around in the moment, rendering it gross, bloated, meaningless.