But, a day or two after a long run, like 18 miles plus, I find I experience the runner's low. It's a general sad, depressed feeling. I suspect I just used up all my endorphins for a while, because soon afterward I am back to feeling normal.
I have learned over the years not to pay too much attention to this particular feeling, because it's not really a sign that something is wrong in my life. Unless you count "running too far" as being something wrong!
Yes, I had it yesterday and today, after a long long jaunt on Saturday. Of course, sore muscles and joints may also play a part in an ambient feeling of misery.
Rhyme of the day:
If running long distance
Is your chief obsession,
Expect to experience
Some brief depression!
Running in general helps control depression:
http://www.findarticles.com/p/articles/mi_m0NHF/is_9_19/ai_86707884
But post-marathon "blues" are common:
http://www.crowathletics.com/id68.html