"People don't want to buy a quarter-inch drill, they want to buy a quarter-inch hole!" Harvard Business School professor Theodore Levitt - If not learned the the last 4 months, I try to remind myself of this sentence each time when working on product communication.
Before you launch your product, make sure it can sell itself. This means that even if it's in the beta stage, make sure your users are able to use it and actually benefit it.
The most painful feeling is checking my analytics and seeing that my returning users are less than 20%