To indulge in the emotions, love, grief, sorrow, despair, emotional joy etc. for their own sake with a sort of mental-vital over-emphasis on them is what is called sentimentalism. There should be even in deep feeling a calm, a control, a purifying restraint and measure. One should not be at the mercy of one’s feelings and sentiments, but master of oneself always.
Ref: Letters on Yoga – II