I'm soon to embark on my third marathon - and second this year. I signed up to run the Baxters Loch Ness Marathon when I was in the middle of training for Edinburgh in May.
I train with Bellahouston Road Runners in the south side of Glasgow and back then I was feeling strong, spurred on by a spree of strong 18-milers I thought nothing could get in the way of a respectable four-hour finish.
But the marathon is a cruel beast. It has the ability to lull you into a false sense of security, comfort you with gentle reminders that you have put in the miles, the training is there, everything, so far, has gone swimmingly.
The determination to beat it becomes all-consuming and you arrive for the race with your kit fully tested and gels round your waste like gun cartridges. For weeks you have stuffed your face with pasta and avoided alcohol and late nights.
You rock up to the start line confident that nothing could have been done better.
And, yet, on the day, it can still all go wrong.
As soon as you cross the line you are thrown into the lion's den. There may be another 10,000 people in bright Lycra and trainers around you, but you are out there on your own, fighting the demons in your own head.
They don't normally launch their attack until at least halfway. And, if you are lucky, the marathon should be a six-mile race. The first 20 should flow in as they have in training: not exactly comfortably, but solidly. You are in familiar territory. You know the places to hide in your mind. Everything between mile one and mile 20 you should have faced on the road before.
But after this, the surroundings start to change.
The people around you take on a pallid complexion. Their gait changes to more of a limp than a run. The pain in your own legs creeps into your brain, gnawing at your will to go on. The beast is biting and there are six long miles to go.
At Edinburgh 2011, things began to go wrong for me 14 miles in. I passed halfway with growing pain in my stomach and a mile later I was hauled up in a Portaloo. I had made an unforgiveable error. With all the excitement the day before I had eaten unfamiliar food. I finished in 4:47hrs.
This year I was back in Edinburgh with more experience in my legs. But the heat and a lack of on-the-move nutrition beat me down, and I crawled over the 26.2 marker in 4:19hrs.
Within weeks I was back building up the miles, once more preparing to battle the beast, aiming for 4:15hrs. There's less than seven days to go now and I can't wait - Loch Ness Monster here I come.
Next week: How I prepared for the race