I am going to be honest here and confess that there comes a point in every run when I would just like to stop running altogether. Either my feet feel tired or my lungs don't feel like working that hard. I'm not alone in this, am I?
I have learned that running is a mental game, so I take these moments to refocus my energy on my pelvis. Thinking of leading from my pelvis, instead of my legs or feet, is a great mental activity and sure does make me feel light and quick. I often see tired runners, and am guilty of this myself, leaning forward or leading with the top of the head. This is bad for the neck and wastes energy.
I imagine there is a large hand behind me gently pushing my pelvis forward. This action helps me engage my upper hamstrings, too, and I feel like I am running faster. And that's always a bonus, even if the speed is all in my head.