I ran 33 miles on Monday. I have never walked or ran further on a single day before. The run was three miles longer than my Winter Tanners in January, but – taking 5 hours and 20 minutes – lasted an hour longer.

My transition to ultra-running hasn’t been seamless; it has required a whole new mindset. The further I run, the more I realise that my body can cope, but the longer I also have to persuade myself otherwise. These 33 miles were a classic example. Two of us had set off along a familiar track adjacent to the Caledonian Canal heading out of Inverness, before turning sharply up Craig Dunain, climbing and climbing until Loch Ness appeared beneath us. We crossed a minor road at Blackfold, following a forestry track that weaved up and down the hills immediately west of the loch.

We gained 501-metre Carn a’ Bhodaich via a sodden, pathless route, with some heather-bashing thrown in. A check of the watch revealed we had covered just 11 miles in two hours. The thought of at least 19 more (our aim was to run 30 miles) and the time that would take dampened any summit celebrations.

The Great Glen Way beckoned. Biscuits and nuts were consumed. We entered our fourth hour of running. The miles ticked over, with the 20-mile mark a welcome barrier. Yet we were beginning to flag. At mile 21 I ran on alone, contemplating the lonely miles ahead. I scampered up to the masts on Craig Dunain without breaking the motion of running. I drank the last of my water.

The view over Inverness and the Moray Firth was marvellous. The brilliance of the day reflected my mood. Running felt effortless. Weather and moods are changeable, however, and by the time I reached the Caledonian Canal with 25 miles under my belt, it was raining hard. I was now very weary. There were two options: run back to the start and end on 26 miles, or turn right along the canal and – with no crossing point until Dochgarroch – almost certainly exceed 30 miles. I turned right and regretted the decision for the next hour.

Passing the 26.2-mile mark was a momentary moment of pleasure, as it had been at the Winter Tanners, but soon after I was dizzy with dehydration, cursing myself again and again for not turning left. I knew it was the right decision to turn left, though. I thought of the Fellsman and I thought of the Bob Graham: tough, sadistic decisions had to be made.

By the time I reached Dochgarroch, my world had narrowed. I felt at peace, albeit a peace accompanied by a raging thirst. In such a state, little things have the power to transform. My little things were refilling my water bottle before consuming my last chocolate bar. Refuelling lifted my spirits – even making me laugh out loud – and I set off on the other side of the canal running eight-minute miles back to Inverness. I shuffled through 30 miles, but the miles thereafter seemed easier. Running again became the most natural thing in the world. What could be simpler than putting one foot in front of the other?

I couldn’t have gone any further, however: 33 miles, with close to 1000 metres of ascent, supported only by biscuits, chocolate and nuts, was my limit. And after running for hours and hours, there is nothing so wonderful as simply stopping and standing still. I was glad. Not just because I’d run 33 miles. But because despite being cold and wet, a little fed-up, very tired and very dehydrated, when I could have run one mile home, I committed myself to another eight instead. I recognised that I was still 30-plus miles and thousands of metres shy of Bob Graham proportions, but I also recognised that I had jumped a level in my understanding of the delicate psychology of the long-distance run.