Suck it up buttercup. Pity parties happen but must not become a habit. Learn to reset quickly & find your toughest YOU. This is a dress rehearsal for your race. Start the run at your normal long run pace and focus on running fast during the warmup. Also, match the course for this run as closely as possible with the course profile of your race. Then nail the 5K Test to keep your paces on track as the plan progresses.