Regardless of how one’s parents have been, one should take care of them in old age in whatever way is needed and possible. Love, tenderness, care and bit of gentleness, a few kind words and assurances are all that the elderly need.
We should ignore the ego they have and the harsh words they may speak. That is their deed. Our attitude towards anyone who is helpless and depends upon us should be kind and a benevolent understanding of their challenges.
Of course, there should be no clinging or attachment in all this. They, like everyone else, are on their own unique individual journey of life. They will and must move on one day. But while they are with us, a few kind and comforting words and sweet gestures can be a good gift from us for them to carry along.
