If you make changes to train.txt and dev.txt, you can retrain the model:
$ cd path/to/CoreNLP
$ java -cp stanford-corenlp.jar -Djava.ext.dirs=lib:liblocal -mx5g \
edu.stanford.nlp.sentiment.SentimentTraining -numHid 25 \
-trainPath path/to/foss-heartbeat/empathy-model/training.txt \
-devPath path/to/foss-heartbeat/empathy-model/dev.txt -train \
-model path/to/foss-heartbeat/empathy-model/empathy-model.ser.gz