Sentimentality is sugar-coating the truth to spare a person's feelings. It is about feeling good right this minute. It is about delaying facing reality.
Love is being able to tell someone the truth even though you know you will hurt them. It isn't always easy but in the end it is always worth it.
"Love is patient, love is kind. It does not envy, it does not boast, it is not proud. It is not rude, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. Love does not delight in evil but rejoices with the truth. It always protects, always trusts, always hopes, always preserves." -1 Corinthians 13:4-7