Yesterday during my run I had intervals on the menu. The first few were fine and I finished them pretty easily. However as the intervals got longer, I started to find myself up against my limits...my mental limits more than anything...the fear that I wasn't going to make it....that I couldn't do it. We push ourselves to our limits but there are times when our limits push back. The key...don't quit!! When they push back, and they always do, use it to fuel your next round but do NOT let them make you quit!!