I choose to believe performance self assessments are useful. Not for, like, my actual job, but they keep me grounded. Nothing like seeing your entire body of work for a year summed up in 30 to 40 bullet points to deflate your ego. Also it gives me a chance to work on my skills in what some of you might consider "lying" though I consider it more along the lines of "creative truth telling" and "having a loose grasp on reality".