[Henry:] "It's not good to know things ahead. It screws up your life."[Clare:] "Yes. But you can't half tell me." [Henry:] "There's nothing to tell". [Clare:] I'm really beginning to panic. "She killed herself." I am flooded with certainty. It is the thing I've always feared most. [Henry:] "No. No. Absolutely not." (1.5.29-32)
Clare's reaction shows that not knowing the specifics of an event in the future make us think of the worst possible scenario, such as death, because we fear the unknown. And we can fear far worse than actually happens.
[Henry to Clare:] "My mother dying… it's the pivotal thing… everything else goes around and around it… I dream about it, and I also – time travel to it. Over and over […] I should have died, too." (1.6.36)
His mother's death still impacts Henry's life because he feels guilty for not being able to protect her, even though he really now know that he couldn't have done anything.
[Henry:] But then I feel guilty for wanting to avoid the sadness; dead people need us to remember them, even if it eats us, even if all we can do is say I'm sorry until it is as meaningless as air. (1.6.4)
Although Henry is not religious he believes that dead people need to be remembered. Why is that? Do you really think it's the dead people that "need us" to remember them, or is it that we need remember the dead?
[Mia to Henry:] "Henry, do you have some kind of death wish?" [Henry:] I consider. "Yes." I turn to the wall, pretending to sleep. (1.7.36)
The blame for his mother's death weighs so heavily on Henry that he wonders if dying is a better choice than continuing to bear the pain of that loss.
[Richard DeTamble to Clare:] "[…] Annette had the most marvelous voice… rich and pure, such a voice, and such range… she could express her soul with that voice, whenever I listened to her I felt like my life meant more than mere biology […] she was a very emotional person, Annette. She brought that out in other people. After she died I don't think I ever really felt anything again." (1.11.102)
Henry's father explains that Annette gave meaning to his existence. Her presence made him feel fully alive, because she allowed him to express his emotions. When she died, his ability to "feel" went with her and now his life means nothing.
[Henry to Clare:] "I can't take this for the wedding. It's too much fun. I mean. Ben's a genius. […] Whatever he's got in here, it plays like a near-death experience." (1.12.164)
Henry seems to enjoy the feeling of being on the edge of death. Given the fact that he continually finds himself near death on his travels, why would he want to feel this way?
[Henry to Clare:] "Whatever happens we both know that I live to be at least forty-three. So don't worry about it." (1.12.172)
Henry intends to comfort Clare by assuring her that it's smooth sailing for them until he's 43. How would your outlook on life change if you knew that you'd be completely safe from death until a certain age?
[Clare:] […] somewhere on the other side of the city Dr. Kendrick is sitting in his office figuring out how to make mice that defy the rules of time. I laugh, but it's life and death, and I stop laughing and put my hand over my mouth. (2.5.13)
Clare realizes that if they don't find a way to help Henry's condition, her babies will keep dying and she might too.
[Clare:] I gather up her reeking, wasted body into my arms, and she is perfect, she is my own perfect beautiful Mama again, for just a moment, […] even as her cancer-laden belly mimics fecundity she rises up in memory, shining, laughing, released: free. (2.6.3)
Clare describes the contrast between the reality of death, and the beauty of the memory of her mother that will live on forever.
[Clare:] It's lying on its back, trying to breathe, its tiny ribcage quivering, but it's too soon, it's convulsing, and blood is gushing from the cord. […] his skin is almost imaginary, […] I can see right through him and my hands are empty and he's gone, gone. (2.12.11)
Clare watches her little baby boy on the verge of life and death, knowing that he's ultimately not fit to live. She witnessed the fragility of life.