I wanted to get out for a run like I wanted a hole in the head...o.k it was not quite THAT bad but you get the idea.
But...I made the commitment to get out 3 days a week and I knew that this was my only shot to make the goal this week. I also knew I would have three days off as it would be impossible to make it out till Monday.
So...out the door I went. I just went 10 minutes out, and 10 back. After 3 minutes I decided to turn the run into what I call a CARBON run. That is where I run hard for the 10 minutes to exercise my lungs and push myself.
It worked and I felt great.
Adding shorter, harder runs between your long runs helps to increase your stamina for those longer runs. You can't exercise your lungs and make them more efficient if you can't talk the entire time.
So mix it up.