Recently, I had an athlete who is pretty talented, (clearly in the hunt for a Kona slot in his AG), push his longer race simulation rides, well beyond Ironman intensity. He did this, and was very excited about the numbers. He should be excited, the numbers were impressive.
Then came his 2 key run sessions in the week, and he was so fatigued from pushing the Ironman bike day, he couldn't complete the workouts. By the time he came back to his weekend race simulation ride, he was feeling a lot better and hammered the ride harder than prescribed again. He did even better than the previous week, so he was really excited.
Then came his 2 key run sessions in the week, (again), and he couldn't complete the sessions, too fatigued again. Again, feeling better come the weekend, he hammers the bike ride harder than prescribed in the training log.
Starting to see a pattern here? A few days later, he tries to push his key run session when he is tired. He tells me, "My run isn't improving." He was correct, his run wasn't improving, because he hammered so hard, he missed key run sessions to address it. When he did do it, he had too much fatigue to make them of any value.
Now he has learned, the key isn't having one awesome/amazing/hammering workout per week, it's having a number of solid/quality sessions you can back up together on a consistent basis.
Darren Smith, one of the top triathlon coaches in the world, told me once, "You get a lot more out of 80% consistently than 95% once in awhile."
If you're digging deep in training, realize you'll get a lot farther by backing off a bit and being consistent.