How do I bear a parent's illness or dementia, when they no longer know me?

Grieve the parent who is already gone while the body is still here; you are allowed to mourn a living person. Do not demand recognition or gratitude they cannot give. Give them a dignified presence — your care is now the honouring. And pray for yourself too, plainly: this is a marathon, and you need enough to reach the end without being destroyed by it. Getting real help is not abandonment.

The commandment is kibud av va'em — honouring father and mother: in these years it becomes not obedience but tenderness, guarding the dignity of one who can no longer guard their own.

From the sources “Do not cast me off in the time of old age; forsake me not when my strength fails.” — Psalm 71