JL, do you hit a point in your running where it seems to get a little easier, or to flow a little better? Can you tell when you've warmed up and hit your stride?
Also, have you messed with changing your stride length or your pace? For me sometimes it can seem to consume more energy to move slower. See how long you can keep a 15 min/mile pace. Are you conscious of how your body is moving -- are your arms moving perpendicular to the plane of your body instead of across it; are you spending too much energy moving up and down rather than forward?
I can tell that sometimes I feel loose and can run well after my 5-minute warmup walk, and some days my joints just feel tight no matter what I do and I don't move as well.
Today I did better. I felt better, I worked harder, I walked less and felt less miserable afterwards. And my average pace reflected it -- 17:17min/mi, officially. That included my warm-up walk and two 3-minute stretch breaks (as suggested by the training app) so my pace while actually running was closer to 15, I think -- if Runkeeper is to be trusted. That feels really slow to me, but if I go faster I can't sustain it half as long.
Two things I did today: 1) Drank a half liter of Gatorade half an hour before heading out, and 2) concentrated on my breathing. I now suspect mild dehydration has been nerfing my performance and making me sore and tight, and I noticed recently that pain tends to make me hold my breath. Bad combination.
So, more fluid might be the key. I thought I was drinking a ton of water before, but apparently the warmer weather is taking its toll.
Oh, also I noticed today that slowing down to go uphill is counterproductive. So you're right about that, Aug Dogg. The trail I run has a good climb to it -- 130 feet over 2.5 mi, mostly in two long stretches of low-to-moderate grade, so the downhill comes just when I really need a rest. But I've found that when I push to get to the top of the hill faster, rather than trying to conserve my energy in anticipation of the length of the climb, it doesn't hurt as much and I can look forward to it being over faster.
Fortunately the 5K I want to run this fall is a road race Downtown, so it'll be pretty flat. I'm hoping that if I train on hilly terrain, by the time I get to the Ribbon Run it'll seem easy.