Whazzup with Mondays???

I don't like to complain, but I've got a quandary - and I'm CERTAIN that this is a typical newbie thing that I just don't know yet.  So, throwing it out to the blogosphere...

Not sure what it is about Mondays, but that first run of the work week has been predictably rotten the past few weeks.  If you just look at numbers, they're fine - good pace (average, anyway) over predictably easy three-mile distances.  Yea to all that.

The reality, though?  That "good pace" is an alternating sprint/gasping walk because I can't dial in a consistent pace to save my life.  The three miles is my absolute limit - I've often got something longer planned (not much longer, but nonetheless I might actually like to get back to where I started, eh?) but once my Garmin chirps that third-mile split, I quit.  Any other day of the week (well, almost - more on that in a second) I can settle on a pace within a mile and I can power through whatever distance I've got planned, but not Mondays.  (And, if it so happens that the first run of the week is on Tuesday, it's as though it's a Monday.  So delaying a day doesn't seem to help.)

My schedule usually includes a long run on Saturdays, then a rest day on Sunday, and I have noticed that the bad-Monday-run pattern seemed to start up when my long-Saturday-run broke five or six miles.  It could be that this is the first time I'm doing any weekly mileage of note - I did just in the past few weeks break the 10 miles per week barrier, since I'm in the last few weeks of training for the You Go Girl! half on September 16th.  (So sad - third time I've run a half, and the first time I've been consistently running more than eight miles per week in my LIFE.  Chew on that a minute.)

Here's the thing - if it's a matter of rest days, I can live with that.  I know my body will adjust to this stepped-up mileage pretty quickly, AND I know there's only about three weeks left until the race and then I'm not tied to these 8-10 mile weekend runs (don't worry, I'm not abandoning them, just figuring I can approach them at a more reasonable pace and be better prepared for the next race training cycle).  My only real goals for this training cycle were (a) consistency and (b) base-building, two things I've never before actually accomplished in my running life.

My real fear, and what kept me up last night, is that it's a sign of overtraining - which I DO NOT WANT with only three weeks left to the race.  And I'm not even sure, if it were overtraining, whether that would make any difference at this point.  What would I do, just rest more?  Cut miles?  I'm about to get there when I taper anyway, right?  Would I do any lasting harm by powering through?

Or... maybe this is the effect of running eight miles (longest ever non-race run, by the way!) early on a Saturday morning, then following it with a straight day-and-a-half canning five dozen jars of peaches and apricots and assorted jam.  That's a lot of standing, which is killer on my legs (WAY worse than running).  So, maybe it's a case of just being stupid less than intelligent about timing my activities. 

Help me here - am I freaking out with cause, or over nothing?  Or do I just need a good night's sleep? (why yes, yes I do.)