Sentimentalism is the working off on yourself of feelings you haven't really got.
We all want to have certain feelings: feelings of love, of passionate sex, of kindliness, and so forth. Very few people really feel love, or sex passion, or kindliness, or anything else that goes at all deep. So the mass just fake these feelings inside themselves. Faked feelings! the world is all gummy with them.
They are better than real feelings, because you can spit them out when you brush your teeth; and then tomorrow you can fake them afresh.