My run ended up starting after 7am. My legs were tired, I wasn't feeling too good. During my first mile I thought about doing a 3 mile run today and a tempo tomorrow (see, that switching thing again). I thought to myself, what if this was a race today? Would I just give up? So, After the first mile I thought I would run about 5 minutes at a faster pace, then turn around and head home. Then I pushed it a little more, then once I turned back to head home I kept pushing myself to go that little further.
Before and during this run I didn't feel great. But having done it, and hitting good times I am so happy I pushed myself. Sometimes you don't feel great, but you just need to suck it up. It's mostly mental. Though, in saying that you need to listen to your body. For me, I know it is mostly mental and I need to work through it.