"User" is a four-letter word.
Of all the taboo sayings in business and development, "user" is one of the worst. It's imprecise, and demonstrates a failure to execute on lesson 2 - that you understand your customer's customer.
Consider the following story:
You're building a website, and have a meeting with the client's project manager to discuss editorial workflows on the back end. During the meeting, you hear her make a simple statement, "I'm not sure this feature will be intuitive enough for our users. Let's rethink it over the weekend and go back to the drawing board on Monday."
In a hurry, you nod your head and make a note. Saturday comes and you look back at the website so you can flesh out alternative approaches - except you have a problem. Which user did she mean?
The site visitor who is consuming the content of the page?
The junior contributor who is preparing content for the page?
The senior editor who is reviewing and publishing content on the page?
The administrator who is controlling access rights for the content?
When you utter the word "user" you are, perhaps unintentionally, abandoning specificity within your project. You might have one particular user in mind today, but what about the other developers and managers at the table? What about you from the future when today's meeting has faded into memory and you're struggling to recall what you worked on?
Don't ever refer to your site's user - refer to the editors, visitors, administrators, writers, and every other type of person who might use your site. Specificity today means ease of understanding tomorrow and clarity of design the day after that.