The War

In the film we see cases of PTS. The first being with Stephen, the dad. He was in the war and lost his friend Dodge. Dodge was already suffering from too much blood loss to survive and was left on the battleground while a helicopter took the surviving soldiers to safe ground. He suffered terrible PTS from the war and that moment of leaving his friend to die. Later on in the movie Stephen was put in a similar situation with his new friend from work. The two men were working underground and a rush of water pushed rocks from the walls and it fell on his friend. The man was going to die but he didn't have the heart to leave him and save himself. He already did that once in the war and the PTS from that incident was to traumatizing to do that again. While trying to save his friend more rocks caved in and injured Stephen which injured him badly enough where he passed away days later.
At this time Stephens son was trying to cope with the thought that he might lose his dad. He was in denial and wouldn't face the situation, he distracted himself. Which is one of the first signs of PTS.

In this film when bad incidents would happen the setting was all similar.
When the dad, Stephen, was hit with the rocks which lead to his death they were in a dark wet setting. They were underground in a cave, it was dark, and flooded with water.
When Dodge was killed in the war it was dark outside in a muddy environment. Its
The little boy Buddy from the other family almost died drowning in an old water tower. He was climbing on this wooden roof on top of the water tower and fell through. Luckily Stew was there and jumped in a saved him a helped resuscitate him back to life.
All of these incidents have a dark, wet, dirty, environment.
In all of these cases the people who lost or almost lost their lives were put in that position doing the right thing. Stephen was there for his friend and didn't want to leave him there to die and suffered death from trying to save his friend.
Dodge was just a man brave enough to fight for his country and died.
The little boy was trying to get the key for Stew for his lock that his brother threw up on the water tower and by trying to do the right thing he almost lost his life.
It seems like the natural course of life takes over and kills these people anyways. Because that's the cycle.