"March Or Die!" - My old BMT PS used to say that.
Seriously speaking, if you are not strong in route marches, try
to stay in front (near the PC or PS) or the first few ranks of the
platoon. If the gap opened up, its easier to catch up rather the
the last few ranks.
Dont gobble down water like a camel during the 15 mins break,
Chances are you ended up puking. Just drink to quench the thirst
and then somemore.
Most likely than not, at the 16km rest point (half and hour or
one hour) Red Bull might be provided, dont tanked up on it. Best if
you keep it till the end of the march or sipped it slowly during
the walk. Same for food (most likely dinner) dont eat till bursting
point.
Dont straight away plonked down and sit during rest points,
Cramps will come inevitably.
Keep your morale up by talking or singing the lame songs. Dispel
the notion that the rest point is still far away, If the feeling to
give up comes in, try to motivate yourself to last till the next
rest point, the next one, then the next point. Before you know it
the march has ended.
Just my 20 sen opinions. I am not a good marcher myself. I had
to fight my brain urging me to stop and sit in the 5 tonner. I
nearly killed myself during a ball breaker march in Crescendo. I
sure missed being 19 again.
Good luck!