Running out of steam

So this stamina thing. It's beginning to get me down. I haven't had two decent consecutive runs in over a month. Every now and then I hit a sweet spot and feel I'm coming out this slump - a perfectly creditable 10k up and down the hills of Enfield a couple of weeks back, a sub-26-minute 5k round Regent's Park about 10 days ago - and then the next outing, it all goes wrong again.
I can't really explain how it feels. I'll be cantering along quite happily when suddenly I just seem to run out of steam. My lungs feel tight and my legs seem to leak energy. It happens within about 100 yards, from starting to feel in trouble to my body just giving up, and the only thing I can do is stop, walk, and recuperate.

Distances that once seemed easy now look unattainable. Times that were achievable seem like a distant fantasy. I simply can't figure what's wrong. So I did what any runner would do in the circumstances. I googled it.
It turns out this is much more of a common condition than I had thought. Typing in "running loss of sta" brings up about 200 different web pages before I've even managed to get to the "mina". 
The internet is great for that, helping you realise you're not alone. The trouble is, it's also great for throwing up about a thousand different prognoses of what might be wrong with you, and a million possible solutions.
So far, I've gleaned that it might be down to "over-training" (highly doubt that, to be fair). Or a change in diet (nope). Or changes in heat and humidity. Or stress levels. Or weight gain (charming, and err, no). Iron deficiency, lack of protein supplements, changes in blood sugar, not enough carbs, too many carbs, lack of sleep, lack of recovery time, too many long runs, too many short runs - all these theories have their supporters.
I've read that runners with this condition should run less, run more, do more interval training, do more consistent long runs, take protein shakes, take iron supplements, take a blood test. And so on and so on. Reading through the list of potential therapies is a marathon in itself.
The one that seems to make the most sense is to me is that I'm trying to do too many long runs at race pace. A consistent theme of the advice is that only about a quarter of my runs should be at that intensity, with most of the rest at an easier pace.
So that is what I'll be trying first - slackening off the pace and seeing if that helps me get my distances back on track. Thinking back to how I trained for half-marathons in the past, I was always more concerned with how far I could go rather than how fast - and that seemed to work. Fingers crossed.
Ending on a slightly happier note, a couple of weeks ago I had the pleasure of taking part in the Golden Stag Mile, which is not (perhaps sadly) a long-distance pre-wedding pub crawl but an annual event organised by Barnet and District Athletics Club. It's an evening of mile races, with the runners divided up by ability, and held this year at the very pretty Finsbury Park athletics track.

I won one of the races last year, largely because I had badly over-estimated my likely running time and had ended up being put in an easy category with slower runners.
This year I was up against somewhat fiercer competition so the pressure was on. The bloke who won (number 227 in the podium picture on the right) was classes better than the rest of us; but I managed to either a) run a perfectly-judged race (if you weren't there to see it) or b) hold on grimly for third (if you were). 
Either way, I got to stand on a podium and have a medal hung round my neck and apart from what I consider the disappointing absence of a national anthem, it was just like the Olympics. Or as close as I'll ever get to it anyway.