Last week I thought I was hurt, so I skipped a run and my running has been better than ever. I only missed ONE scheduled run, but it meant 4 days of rest for my legs. It was apparently just what my body needed, because I've been running stronger and faster since. I did end up making up the run somewhat on Sunday, but I didn't go running that day with that intention. I was just feeling good and wanted to run for fun, so I kept it short and easy. I didn't even bring my iPhone. I just ran and enjoyed it.
So remember that when you feel worn out, either physically or mentally, and your body is telling you (or screaming at you) to take it easy, you should listen because missing one run is not the end of the world. It's insignificant compared to the vast number of runs you do in the course of your training cycle and it will help you run that much better the next time. It's about prioritizing your goal. If your goal is to get fit and lose weight, doing more cross training may be fine. But if you have a target race and a goal you want to beat, then making those runs the best they can be is the priority. Everything else has to enhance that, not deter from it.