Why does the poet smile while bidding goodbye to her mother?

When the poet reached the airport, she looked at her mother who was pale and old. She was suffering from aches of old age. The poet kept smiling and said, 'See you soon Amma'. The poet could do or say nothing much but smiled at her mother because she her mind was filled with thoughts and fear that she might not be able to see her mother alive the next time she visits the city. Her pain was reflected in her smile which was plain and devoid of real happiness. The poet was choked.

Regards