Running eye, you should take heed of your last line. You shouldn't feel like that, and that's a sure fire sign you're overdoing it pace wise in training.
If you have the patience, you can comfortably lower your pbs and feel fresher into the bargain.
Off your pbs, even the half marathon one which you seem to be counting from training, the pace zones i gave prreviously sound about right.
Therefore, if i were you i'd slow the easy pace running down immediately to the 8.20+ zone.
Similarly i also think you're overdoing it in the speedwork.
5miles at 10k pace is a monumental effort. You might as well run a race then do that.
As for that 6.10 pace x3 , with 1/2mile 7.45 pace, I'm not sure what the thinking is there?
6.45 is your 10k pace, so 6.30 at fastest would be your 5k pace, so what is 6.10? Probably 3k pace?
Doing 3miles at 3k (1.8mile) race pace is too much. To make it even more challenging, you don't even give yourself a standing recovery, instead doing 1/2mile at easy pace!
A better session would surely be 3x1mile at 10k pace with 2min recovery. That would still feel a challenge. I can only imagine how wrecked you must be after your one!
If you want a session that will feel medium hard, i'd do the 10mile session of 3miles warm up, 6miles at MP, and then 1mile cool down. It's a session that's never easy but gets you worked out, without needing too much recovery time.
Therefore, i'd suggest slow it all down, add that MP session, and try and add 10miles to your total basket over the next couple of months.
On coming through without any problems, you can probably then think about adding a speed reps session to go along with the tempo. This session would be based on your calculated times, and dependent on the target
10x800 at 10k pace, 3x2mile at HMP, etc
Edited: 28/07/2012 at 20:21