In Episode Eight of WandaVision, when Wanda discussing her mourning the death of her brother:
Wanda: It's just like this wave washing over me again and again. It knocks me down and when I try to stand up, it just comes for me again. And I can't... It's gonna drown me.
Vision: No. No, Wanda
Wanda: How do you know?
Vision: Because it can't be all sorrow, can it? I've always been alone so I don't feel the lack. It's all I've ever known. I've never experienced loss because I've never had a loved one to lose. What is grief, if not love persevering?