"He kept the details of his work to himself, as if they were all some desperate secret" - Why does Mark do this and what is the effect on his relationship with Elena?.
As a war photographer Mark is constantly dealing with issues that deeply affect him. Resulting from this is his extremely secretive nature, which restricts him from being able to share his experiences with his lover, Elena. His efforts to protect himself and Elena in conjunction with his ever-growing guilt, are the major factors, which contribute to this secretiveness, which ultimately threatens to destruct Elena and Mark's relationship. .
Mark feels that if Elena were to know the 'real' truth of what happens in the field, she may be hurt and distressed as a result. When he tells her of the reality behind Stewart's death on the job, he follows this up by telling her "Why do you think I don't tell you what happens out there Why do you think none of us talk about this?". Mark knows that Elena worries about him when he is away, so as a means to protect her and ease the burden of her anxiety, he keeps the painful truth away from her. Mark witnesses some extremely horrific incidents as part of his job and reliving these with Elena is just going to re ignite these agonizing memories. By keeping his home and work life separate to ease his pain, Mark creates a divide in his life which amounts to the creation of many secrets. .
When Mark is on the job, he feels as if the camera serves as a barrier, protecting him from both the physical and mental ramifications of what is unfolding in front of him. He seems a very cool and calm sort of person that may have trouble expressing what he feels, preferring to bottle it all up inside. He wonders, "How did you ever tell anyone any of this? Because once you started telling, there was no place to stop. One story, one pain, bled into the next, and they spilled out until there was nothing left to hold".