You can grieve before someone finally passes. My grandma lived well into her eighties. Her final two years were not great but we did what we could to make it better for her. When she passed it felt like a good part of feeling for her hardship has already passed, together with the relief of knowing that she is no longer suffering.

Grieving is important. To do it properly be close to those who need it. Dying is a process and not a moment. Be there for those that need it and give yourself room to do it properly as well.