The reason could be that in the first stanza, the poet conveys about joy. This depicts that India was coming out of British Rule, with a new freedom being born. In the second stanza of the poem, we can can understand both sorrow and joy were present. Here, the poet wants us to understand that there was happiness but some grief was still left. In the final stanza, the poet grieves about those people and fighters who lost their lives in the freedom struggle.