
The heat has definitely been a source of my de-motivation, but didn't explain my lack of "oomph" or occasional bonking on easy rides. After talking to my brother (currently attending medical school), and doing some reading I've concluded that I was slightly anemic!
"Most commonly, people with anemia report a feeling of weakness or fatigue, general malaise and sometimes poor concentration." That summed me up pretty good.
My family has gone vegetarian this year. We'll have the occasional fish, shellfish or chicken when eating out (like at the Chinese food buffet), but for the most part eat a somewhat vegan diet. Very little dairy or eggs.
Vegetarians and Vegans, take note!

"Vitamin B12 is important for the normal functioning of the brain and nervous system and for the formation of blood. It is involved in the metabolism of every cell of the body, especially affecting the DNA synthesis and regulation but also fatty acid synthesis and energy production."

My brother said that B12 deficiency is common among vegetarians and vegans, and also explains why you see some of these people carrying around some extra weight regardless of their healthy diet.
My brother sent me a bottle of B complex supplements which I've been taking all week. The results this far have been really good. In fact I felt stronger yesterday than I've felt in quite a while! I've also lost a little fat off my midsection, but I'm not certain if this a result of the vitamins or the fact that I've been out of beer for most of the week. Time will tell...