Whose truth, I wonder? Is honesty always the best policy? Well, yes... and no. Like all great questions, the answer is invariably 'it depends'.
It might be honest to say that shirt looks terrible on you. It might be honest to say your driving is terrifying. It might be honest to say the report was appallingly written.
More often, it's not what you say, but the way that you say it.
The sandwich model of feedback used to be popular - remember? Say something nice, then add the criticism, then finish off with something nice. The trouble is, our brains only hear the criticism and the rest feels like hypocrisy. The intent might have been to direct or correct, but the impact can have quite a different result.
So, what to do? Before you speak honestly, think about the impact of what you're planning to say. What's your intent in speaking? Will it be perceived and received in the way you want it to be? How else can you say it?
Perhaps a better approach to honesty might be the truth with good intent. Try filtering what you want to say through the ancient Sufi Four Gates of Speech - Is it true? Is it kind? Is it necessary? Is it the right time? If your answer to any of these four is no, then think again about how you say it.