Wow. Expected you to be heavier, you really achieved serious results with your diet

So, about my army experience. My height is 173 cm, and I weighted 86 kg at the beginning of a young soldier`s course. And wasn`t really into sports too.
The first obstacle wasn`t even tiredness or low strength or something... Boots! I`ve never worn something like army boots in my life, and they ripped the skin off my feet really fast - literally, 3-4 holes on each foot. Combined with physical weakness, this resulted me being last in every run - even in usual morning jogging with the unit. Just imagine - you are running last, and your formation is farther and farther ahead... Feels bad.
At the end of the course (2 weeks) I weighted 75 kg. My feet were still killing me, but at least I learned to keep with the formation. But the FUN was in future - I was distributed to the batallion with the craziest officers in the whole regiment. For some unknown reasons they ALL liked "march-throws", long speedy crosses with all available equipment.
So one winter morning (approximately after one month of service) we just took everything and ran to nearby forest. And this is where I felt the lungs hurting... After like 3 kms I was breathing so loud that it could be heard in another end of a column, and somebody of the seniors said "Looks like we`ll be carrying his body back soon". He was wrong
Soon I realised that running in the head of the formation is more profitable, because of short stops to wait for guys running last, while when you are last you are always chasing the formation and never stop for rest. To make a story short, there were 8 young soldiers running, nobody was specially trained before the army, and one month is obviously not enough to develop some serious stamina and muscles. But we all managed to endure all 15 kms, though one guy almost fainted near halfway and we took part of his equipment.
My advice is still the same - overcome the pain, you can always endure more than you think. In your age and with your constitution it is very hard to be killed with a single mile