It seems like, whenever I hear a writer talk about how unsentimental he is (and it usually is a he), something pretty schmaltzy is bound to follow. If a macho intensifier ("relentlessly," "unflinchingly") is used to modify "unsentimental," then get ready for pure treacle.

Don't worry about un/sentimental. Just write interesting or affecting words, and deal with it in revision. What you resist persists.