Bi-polar Runner

On Monday night I did an hour long run which included a 2-mile time trial. I generally do these time trials once a month during the earlier phases of my training so my coach can judge my progress and set my paces.  The TT went surprisingly well. I felt strong and pushed myself just the right amount. I completed the 2 miles in 15:18, for a 7:39 pace. This is a decent improvement over my previous best of 15:51 (7:55). I was ecstatic and for the rest of the run I fed on that feeling and told myself "days like today are why I do this."
Fast forward to this weekend's long run of 1:40. I felt like two cement blocks had been strapped to my legs and my lungs felt like I had spent the weekend smoking. Unlike Monday, the thought running through my head was "why do I do this to myself." It was incredibly disappointing.
Why does that happen? How do I find consistency? And by consistency, I mean consistency in feeling good not feel like crap in motion. I suppose I could attribute the lousy weekend run to the accumulation of the week's workouts. I can understand not feeling 100% after a long week of work and training, but should it make THAT much of a difference? Maybe it should. Or maybe it does for me, but shouldn't. I know everyone has good days and bad and I should not expect to be the exception to these rule. However, I would think that a bit more consistency isn't too much to ask for.  What am I missing?
On another note, I have begun to use the Trigger Point hip and lower back kit to deal with my piriformis pain. I've only done it two or three times and while I haven't noticed a huge difference in my day-to-day discomfort, I do feel significantly better after I do a session.  I'm not sure how often I should be doing it, but I'm going to keep at it at two or three times a week and hope for continued improvement.

Training totals for 1/10-1/16
Swim - 6300 yards
Bike - 58.5 miles
Run - 23.4 miles
Plus one hour of boot camp and two trigger point sessions.

How do you know?

Yesterday I ran the 12Ks of Christmas in Kirkland. The 12Ks of Christmas is a play on the 12 Days of Christmas, which each K representing one of the days...three french hens, etc. You'd think that would be pretty obvious, but you'd be surprised at how many people were confused by this concept.
Anyway, I digress. It was a fun race and the weather was beautiful...clear and brisk. I felt good and the race went well. I'm not sure what, if anything, was off and yet I still believe that I am capable of running faster than I did. Was it because I was just training through it? Was it all those bloody hills? Just what IS the trick?  How do you know how fast you can truly go? What are your true limits? I wish that I could have one perfect day when, at the end, I would know that was it. That was as fast as I can go and that is the gold standard. But there is no way to know is there? You will always wonder...even if you meet your goal, set a new PR or feel like a super star all day.
I have also decide that someone needs to create a magical formula in which you can plug in your hours of sleep, the week's workouts, nutrition, weather, mood, course, your bathroom habits, etc. and out would come a predicted race time. Surely some super computer could work on that.

What have I done?

I don't think the magnitude of what I did this week has really sunk in, nor will it sink it for a while. On December 1st I registered for the Beach2Battleship full iron distance race. It was inevitable, I think we all knew it. But it is official and now I'm going public.
This morning I went on a longish run with two lovely ladies, Heather and Christy, who were kind enough to invite me along on their traditional 9 miler through Golden Gardens and Discovery Parks. I was stoked. New running friends, new route and it was sunny to boot! Well, my run was rubbish and I was embarrassed in front of what I hope to be new running partners. Of course there is nothing like a crap run to plant that lovely seed of doubt in your mind when you have just committed to doing a full bloody iron distance triathlon.
Am I in for it?