The best messaging has the courage to be incomplete. Don’t be all things to everyone.
For example, if you’re doing an email marketing campaign, don’t tell potential customers the zillion things your product or service will do for them. Instead, pick one or two powerful messages, and leave it at that. You may miss out on some customers who aren’t looking for what you communicated in those incomplete messages, but that’s OK. Instead, your message will be heard by a few other people who do buy. If you don’t do this, your messages will look and sound like every other message, they’ll be instantly forgotten, and you’ll wonder why you can’t sell anything via email marketing.