<human>: I did my first ever 7 mile run yesterday and felt like I could go miles and miles further when I was done.  The person I run with was extremely exhausted by the end of it and started to slow down a lot the last two miles.  We've run 4-5 miles a handful of times and I'm the one that is normally cursing the world at the end of it while she could keep running.  

I thought this was pretty weird since she is much better at getting the other days of running and other cardio in training for a half marathon while I am normally too exhausted after lifting to do the full amount on our plan.  

On the 7 mile run I figured I needed a boost before hand so I had some amino energy, and sure enough by the end of the run I felt like a million bucks.  I was also pretty pumped to set a personal best for distance in one run though too.  I was wondering if the reason I felt so much better even though I ran 2 miles further than ever before was the amino energy, the excitement from setting a personal best, a mix of both, or neither?

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<bot>: How helpful is amino energy in 'longer' (7 miles which I know is child's play to some on here) versus the adrenaline of setting a personal record by two miles?