It's not always easy to give someone negative feedback, especially when you have to do it over email. If you can't explain your feedback in person, this one little word can keep it from sounding too harsh. When you write your feedback email, Jocelyn K. Glei, author of Unsubscribe: How to Kill Email Anxiety, Avoid Distractions, and Get Real Work Done, recommends you use the word "yet" whenever you can. Glei explains at Harvard Business Review:
Note the difference between saying: These designs are not where I want them to be. Versus saying: These designs are not where I want them to be yet. As psychologist Carol Dweck has argued, by adding that one tiny word you put the recipient on a timeline of learning and achievement rather than making them feel like a failure.
"Yet" keeps the focus on the future and progress. It also says that you care about their growth as much as you care about the work they're doing. You avoid sounding over critical, and it keeps your recipient from getting defensive or feeling defeated.
How to Give Negative Feedback Over Email [Harvard Business Review]