Based on the available evidence, if you want to write one of the fifty most important novels in the next half-century, then by all means avoid sentimental language. But if you want to get published, sell books, be reviewed, win a prize or simply make someone happy, then emote away and just write a good novel. 

Over at The New Republic, two professors use sentimental analysis to uncover how sentimental vocabulary is used across various literary genres and historical periods—and whether it makes a difference in how seriously a work of fiction is taken. Their findings might just surprise you.