Daily Boredom
Given that each side's front line was constantly under watch by snipers and look-outs during daylight, movement was logically restricted until night fell. Thus, once men had concluded their assigned tasks they were free to attend to more personal matters, such as the reading and writing of letters home.
Meals were also prepared. Sleep was snatched wherever possible - although it was seldom that men were allowed sufficient time to grab more than a few minutes rest before they were detailed to another task.