Fear no more the heat of the sun

The saying "fear no more the heat of the sun" comes up repeatedly at various points in the novel, both from Clarissa and Septimus' points of view. After a little bit of research, I discovered that the quote is from Shakespeare's Cymbeline, and it is said as part of a funeral song in the play.
In Mrs. Dalloway, Clarissa first encounters the quote through a shop window that displays an open book. At first, this quote may seem confusing or unimportant. We have just met Clarissa and are beginning to learn more about her personality. However, if you look at the quote from the broader scope of the novel as a whole, it is very telling. Right before she sees the book, Clarissa thinks about death. She asks if it mattered that "she must inevitably cease completely", and asks "did it not become consoling to believe that death ended absolutely?" Clarissa, until the end of the novel, seems to fear death. Or, on the contrary, she seems to enjoy life thoroughly, saying "what she [Clarissa] loved was this, here, now, in front of her". Clarissa seems to find comfort in reading the words, "fear no more the heat of the sun" especially in the face of adversary.
Another similar instance occurs when Clarissa is disappointed after hearing that Lady Bruton has asked Richard to lunch. Lady Bruton is someone Clarissa looks up to, and she wasn't invited to Lady Bruton's lunch. Again, Clarissa looks to Shakespeare for comfort, repeating the line from Cymbeline. We also return to the image of death as Clarissa describes herself as feeling "suddenly shrivelled, aged and breastless" and notes her failing "body and brain", both of which are direct results of Clarissa not being invited.
Similarly, Septimus refers to this line of Shakespeare for a sense of comfort. As Rezia makes hats, the frightening images he sees, such as the dogs barking, fade "far away on shore". Septimus can finally relax, and "fear no more", as he relishes the golden beauty of nature in that moment. However, a mere few pages later, he commits suicide. Perhaps "fear no more" was not referring to Septimus' suicide directly, but Woolf seems to constantly put Shakespeare's quote in proximity to death imagery.
The last instance occurs near the end of Clarissa's party. She contemplates Septimus' death in a separate room and then watches the old woman go up to bed and turn off the light. Besides the obvious presence of Septimus' death, I think Woolf created additional death imagery with the old woman. She closes the blinds and turns off the light, and Clarissa watches her intently, saying "fear no more".  It seems that Septimus' death and the old woman have provided Clarissa a frame of reference to what life is, and she accepts the fact that she will die one day. The line also gives her the courage to face her past (literally), despite her regrets about it, and return to Sally and Peter.