Got a difficult email to write? Start with the truth. Boss asked you to write the marketing department and tell them they're not going to get their new features? Start with the truth.
Need to back out of making 48 cookies for the bake sale? Start with the truth.
Need to quit your job? Start with the truth.
Want to say no to the big deal? Start with the truth.
Dying to tell the handsome fella you've been seeing for a few months that you love him? Start with the truth.
Okay, so start with the truth, then what?
Start with the truth, then edit.
This is my best writing advice for writing hard things.
Take a breath [or 10], clear your brain cobwebs and just let the truth pour out. Don't edit as you write. Let it all fall out.
When you're done, revisit and edit. Step away. Edit 5 minutes later, an hour later, or after a week. Whatever it takes.
Pro tip: if it's an email, populate the recipient email address after you've finished the message.