So, I've been running really well recently (at least, for a freshman), and I've been going the extra mile. Last week, I went to cross country camp, and I did really well. This week, when I was running, I did take one day off, so I wouldn't die, but I've just been generally doing horrible this week. Just now, I did 10 minutes easy run and was going to go into a 3 minute sprint, and I stopped after 30 seconds. That's literally never happened before, not even when I was starting up. Throughout this week, I've had to start walking again, and even do 20 minute easy runs rather than my normal 40 minute ones. I haven't been hurting at all, and I guarantee that it's not a lack of motivation. I just found that I couldn't do it anymore. What's wrong with me? Has this happened to anyone else?