Training observations

In the last 8 days I have cycled 430 Km's on my MTB over 7 rides. That's 23 hours of riding. On the face of it it's a reasonable amount of training but in context of the upcoming race it's an average effort. What is worrying is how tired I feel.
Last Saturday I rode 200 Km's on a Mini Munga ride with a handful of other Munga entrants. I struggled. If Anne Robinson was around she no doubt would have quipped "You are the weakest link, goodbye!" To add insult to injury she may well have recycled one of her more acerbic but fitting insults, "Who, alas, has delusions of adequacy?"
I am grateful to have a job and while it puts food on the table and pays the bills it makes it challenging to rack up significant saddle hours. To make up those hours I have been riding during my lunch breaks as well as riding at night. The lunch rides are of a short duration, 1 hour, but should slowly get me more heat adapted.
My performance riding at night is in stark contrast to my day time rides. Once the sun goes down and the mercury follows suit I am invigorated and ride a lot faster and harder. Perhaps my cold adaption over the last few years is deeper than I thought. My inability to ride strongly in the heat needs serious attention. Hopefully the ride at Mankeke in a fortnight will help this adaption.
The constant tiredness is also concerning. Over training comes to mind but is that really the case? Exercise gurus will advise you against increasing your training load by more than 10% per week. Going from a single weekend ride of 50 Km's and increasing it slowly in accordance with good sense guidelines can get you all the way up to 156 Km's a week over 3 months - whoop whoop!!
That won't work. The answer, I suggest, it to deliberately over reach without over training. Most people are familiar with the idea of over training but haven't heard of over reaching. Over training in a nut shell is training so hard that performance becomes progressively impeded to the point of requiring weeks if not months of rest to recover. Over reaching by contrast requires one or two days rest to recover. When you are training regularly it's hard to take a day off. The idea of two days without training seems completely insane. Balanced carefully with adequate rest overreaching can help you increase your weekly training hours without pushing you into an overtrained state. For me it means 2 rest days at the end of each week. It seems to work as I have increased my workload a few hundred percent and after a few days rest my small time trial rides show my speeds are increasing. If they were headed south I would need a serious rethink. As I sit here now wishing I could go for a ride I know that being off the bike today is in fact the best form of training possible right now.
By the way, after a 2 day rest following the Mini Munga ride thoughts of Anne Robinsons trenchant criticisms no longer haunted me.