Good runs, Bad runs!

This is a subject that I think every runner has pondered at least once during his or her running career.  What in the world causes these spectacular runs and these terrible runs?  I had the most spectacular 4 mile run this morning.  It was an easy run day ( I am trying to stay in training for another Half marathon in September) so I started out at what I thought was a leisurely pace, which for me is about 13min or more per mile.  I am feeling great, just running, not doing my walk/run.  I wore my watch, but didn't really pay much attention to it, just wanted to make sure I did the 4 miles.  I never slowed or felt like I needed to slow down....the whole run was absolutely effortless!  When I was done I did look at my watch and I ran the whole 4 miles in 50 minutes!  That is a little over a 12 min. per mile pace, which for me is fantastic!  I have not run 4 miles without any walking in a long time.  I had a 3 mile run like this a few days ago also.  Problem is, I had the most awful run I can remember just a week or so before.  So what causes this phenomenon?  I don't change anything.  I get the same amount of sleep, eating habits are the same, work is the same.  Some days I go out the door and the minute I take one step, I know it is going to be a bad day, then there are those days like today.  What the heck?  Why don't I ever have days like that when I am doing a 5K or a Half?  I have never felt that good during a race, never!  I have noticed that the really good runs usually take place when I don't feel like going, but force myself out the door, probably to make me realize that I should be running!

Anyway, I just wish there was a way to bottle whatever it is that causes these great runs, because I could sure use it!  I have had some pretty miserable moments during my Half marathon career.  I realize running 4 miles and running 13.1 miles is a lot different, but you know what I mean.  If I could figure this out, I would probably become famous!  There just seems to be no rhyme or reason, just go with the good runs and be thankful!!!!

Ginny