Running

The HM valley of desperation. 

The mentality hardest part is between 10th and 15th km. You feel tired but too much km are still missing. 
Train to overcome those negative thoughts and keep a “relaxing pace”. 

Then at 15th you can just put out everything you still have and it’s mentally downhill.

My latest half looks quite different. I’m more of a slow starter and I also don’t like spending too much energy navigating through the packed crowd that you inevitably encounter during a race start

Where are the other splits above 13th?
You have a good approach. 

But I was going for a PB and started from grid1.

I found it to be 30km (75%) for the full marathon. 

30 km with your legs
10 km with your head
2 km with your hearth
195mt with tears in your eyes

Seems like the 66% mark is mentally the toughest for any race distance.