In the last couple of years, I am 53, I have struggled with often having terrible training days. I would head out the door and feel like crap from step one and end up turning around and walking home. If I didn't quit, I would run incredibly slowly for a few miles. The bottom line is I never felt recovered and often felt more tired than I should have. I had come to the conclusion that age had finally caught up with me.
In the last couple of months I have come up with a schedule that really seems to work for me and I haven't had any bad days since I started. It might work for others in the same situation.
The schedule
Day 1 w/u 2 miles 4-6 mile tempo + 2-4 200's
Day 2 w/u 2 miles 10x 1 minute hard/ 1 minute easy. Will increase to 20x
Day 3 - 30 minute walk
Day 4 30 minute easy jog
Day 5 - long run
Day 6 - 10x 1 minute workout
Repeat
I am doing 2 semi-hard,(for me) runs in a row. But the reason I don't feel tired is because 1.they are working different systems and 2. the two day lag rule. I feel sore/tired from day 1 on day 3 when I am just walking and feel tired from day 2 on day 4 when I do the light jog.
Sorry for the long explanation but the bottom line is that it brought me from the point of being ready to pack it in to feeling good on most runs.
The only question at this point is can I race well off this schedule...but even if I don't race well I will feel much better in my training