The key is to stop frequently when you do heavy exercises for example carrying heavy burdens. Set yourself short goals to reach, then stop and start over again. The folly of forced march can not be over emphasise. Don't do them unless the dearest emergency. For it you meet troubles or expect troubles you should meet it fresh.
Tired men make mistakes of judgement and timing.
Weary bodies fall easy prey to the parasitic infections of the wild valleys. When walking on a long stretch beside resting a lot, one should be careful of his drinking habit, as you walk rinse your mouth with water then spit the residue out, it is another lesson in the syllabus of survival. A tired man can not march with liquid slopping around in his stomach. Plastic rope can be used for shoes laces, insuring you to have at all times a rope for many usage, tying up whatever you want, from hooks to bones to tent etc., as fishing line or as snares etc. Beside burning and giving a high heat, the rope does not rot and it can be unravelled to make longer rope as need comes along.