Slogging through the miles

I must be getting old.  Well, okay, I AM getting older; that is a truism, and nothing I can do will reverse it.  But I'd like to get old a little bit more gracefully, and not trip and stumble into it.  Yesterday's run makes me feel like it's happening more like the latter than the former.  The plan was for 12 miles with 7 miles at half-marathon pace.  Sounded like a reasonable hard run, and I was feeling pretty good as I started out.  When I looked at my watch, though, it was feeling pretty hard to run at an easy pace.  I decided to just run 12 at long run pace.  And I kept getting slower and feeling worse.  I finished my run at a bit over 11 miles (loop course), and was pretty thankful for being done.  I seem to be getting slower and losing fitness, rather than gaining fitness.  In mid January, after being in Taiwan for nearly 2 weeks, I ran a 10 mile race at 6:45 pace, and felt pretty good, even negative-splitting the race.  Yesterday, I ran nearly the same distance at almost 1 minute/mile slower, and didn't feel like I could run any faster.  Between that run and my long run disaster from a couple of weeks ago, I'm starting to panic about Boston... more than a little bit.  I guess the good news is that I can still run a respectable race (relatively) if I run my long run pace for the entire marathon.  That, and it was relatively warm and sunny when I was running yesterday.  Well, today is my day off from running, and tomorrow is another day, so we shall see if things get better.