[header] How to tell the truth when it hurts [title] Ask permission. [step] It's a good idea to let the other person know you're interested in having a tough conversation so that they don't feel blindsided. Ask if the person is willing to talk to you. 
If the person says no, allow him or her to have a bit more time, and then ask again. Sometimes people need time and space to process that someone has something potentially painful to say.