However being older and wiser doesn't always work. I started back to running again in August 2002, and by December 2002 had run 10k in 39mins, and April 2003 10M in 64mins, and thought that I was about to launch into a spectacular MV55 career. By the end of June I was struggling to break 40mins for 10k and 66mins for 10M. What I had done was to abandon my steady running/one speedwork session a week regime for one which was based on about 50 miles a week of relatively fast running everyday together with a tempo run and and interval session. Within two or three weeks my running developed a "boom and bust" charactor. I never knew from day to day how the session would go, if it wasn't going well I'd still try to run it fast rather than backing off. Gradually the "bust" sessions and races became more predominant and the downward cycle started. By the end of July 2003 I was in the same state, that I think you are now. At the time I was too close to the problem and couldn't see the cause - quite simply not enough structure within the weekly cycle, the obvious idea that hard days need to be balanced with easier recovery days. Because of my rapid improvement I had blurred the gap between "training expectation and racing realism" refered to earlier.
What I did was to take a week off, but said to myself that if I wanted to go for a run I should, but that it wouldn't be longer than 5 miles, and initially I wouldn't go for more than three consecutive days without a rest. I started this at the beginning of August 2003. By the end of August I introduced a fartlek session and a tempo run of 3-4 miles, and only did these runs if I felt like it. Gradually through Sept and Oct these sessions togther with the long run crept up - under there own imptetus, rather than by me forcing it. At the end of October I ran a HM clocking 82ms passing 5m in 31 mins and 10M in62mins. At the time I didn't have a clue where it came from. In retrospect I think that the potential to run that fast was already there in August, it just needed a little gentle nurturing back onto the straight and narrow.
Looking back over this, I’ve rambled on, and I'm not even sure its of any benefit to you. One thing I do suspect however, is that your problem is nowhere near as desperate as you think it is, and that with a bit of " gentle nurturing back onto the straight and narrow", you'll be running as quickly as your training equips you to, long before the end of the season.