With death came grief. Molly Weasley learned this the difficult way. Then again, there's no easy way to deal with death. No matter the circumstance, death is a situation that wrenches at the heart and affects the mind. Death is the circle of life closing. Nothing can prepare a person for the end of life, even if it's expected and planned for.
When Gideon and Fabian die, Molly's beloved brothers, she cannot help but cry. She lets out helpless, agonizing sobs when she thinks nobody is looking. Arthur, oblivious that he normally is to his surroundings, can tell when she's at her lowest. This is what marriage is about: noticing when you're down, and bringing you up. He puts his arm around her shoulder, and coos. It's childish, but his presence and his voice is comforting enough; grief stabs her in the heart, the most vulnerable part of her body. Molly can face the day now that Arthur reminds her that she can face the day. She cleans as if Fabian and Gideon are alive to remind her that she's working too hard.
When Molly hears of the death Lily and James Potter, she fears for their baby son Harry's life. She isn't sure about these Muggle relatives of Harry's. Her maternal paranoia kicks in at the worst times, especially when she's unsure of something. She feels conflicted. On the one hand, she wants to grieve for Lily and James, something she feels like she's doing wrong. She didn't attend their funeral, and she hates herself for it. She missed out on closure that would've been provided by a casket. She still tries to make time for There's a lull in the wizarding world, as He-Who-Must-Not-Be-Named has been defeated for now. Molly and Arthur are grateful for the time to raise their children.
Eleven years later, Ron goes to Hogwarts, and the nest is beginning to feel empty. This is like a casualty, except without death and destruction; it is still a loss Molly has trouble coping with, regardless. When Ginny finally goes off to Hogwarts, the nest has officially emptied out. She seems much more distant after a few weeks. Her letters get shorter and shorter, and it isn't until she resurfaces that Molly and Arthur learn that He-Who-Must-Not-Be-Named possessed her via a diary she wrote in. Harry saved her, and Molly trusts him so much more. Molly protects her daughter much more fiercely now than ever.
When He-Who-Must-Not-Be-Named returns to power three years later, everything seems to go to hell. Casualties are the worst in times of war, and that is something she nor Arthur cannot ignore. Sirius Black died from the veil, and surprisingly it's Arthur whose tears fall, who needs comfort and support. They are used to death by now, but it's still not fair. The Order of the Phoenix has died, not because of chaos but because of death; Molly's heart constantly hurts thinking about. The world seems to stop and start when Dumbledore dies.
The final battle has started, and it's about time; everything seems so confusing and strange and utterly gloomy. Dejection is everywhere. When Remus and Tonks die together, arms clasped together, Molly copes with their death by worrying about Andromeda and Teddy. The world seems to stop when Fred dies. His laughter repeats in Molly and Arthur's minds, and it is a cruel reminder of what could've been. George hasn't smiled since. George might never smile again. Molly can't, won't be okay with that. She loves him more than ever now that Fred's gone, and won't ever come back. Arthur hurts, too; Molly, and Arthur grieve in sync.
No matter how many casualties Molly has faced in her life or how many casualties she will continue to face, she will always come out a little bit stronger. In return, she will become a little less soft. Arthur has to remind her that's the proper tradeoff.