When you meet up with a friend you haven't seen in three years, you wouldn't immediately say, "You look 15 pounds heavier." Why not?
Doing so would be tactless and cruel, so instead you say something like, "It is so great to see you again," even if you think to yourself that your friend looks a bit on the heavy side.
People say that honesty is the best policy, but that's only true if you also show compassion when sharing an honest opinion.
In a civilized world, honesty and compassion need to go hand in hand.
You must use honesty to help other people, not to hurt them.
And you must be cautious not to accidentally harm others.
Here are a few tips how to do this...
Recognize that humanity is more important than the absolute truth.
Use facts to help another improve his or her life, rather than to do something that might destroy their life.
Recognize that the "truth" is always subjective. Each of us sees "facts" through a haze of beliefs, attitudes and experiences.
Ask more of yourself. The best skill, is bringing out talent in others, so rather than judging others, do your best to help them.
Share constructive feedback with tact, and do it when the other person is ready to hear it.