In Do Androids Dream of Electric Sheep?, author Philip Dick imagined a society where people regularly took drugs to change their mood.
The only two pills I personally take are vitamins and the occasional Tylenol. I love my morning coffee, enjoy a dose of chocolate every couple of days, and probably have one alcoholic drink a month, on average.
But I realize that I am increasingly using my Ipod (with no music, mind you, just podcasts) as my personal mood regulator. I listen to IT Conversations when I want to build a healthy motivation and "white collar" work level, including driving to a meeting. I listen to political commentary when I want to physically rev myself up, say when doing yard work. And I listen to movie reviews at the end of the day to wind down.
I noticed a similar trend in myself when I started organizing Internet bookmarks/favorites by day of the week. Some clicks were better for Monday, and others for Friday or Saturday.
I believe this kind of mood awareness/engineering may become increasingly relevant for both deploying personalized learning programs and even planning formal learning events.