Tact isn’t lying. It’s truth that bothered to put on shoes before leaving the house.

Being blunt and being honest get confused with each other constantly. Delivery is not content: you can change the order, the timing, the words around it, and the thing you are saying stays exactly as true. What tact removes is the part that was never information in the first place, which is usually your irritation. People who call that dishonest are often just attached to the irritation.

Take something true you need to say and write it twice. Once as it arrives in your head, once as you would want to hear it. Say the second one, and check that nothing important went missing between the two versions.