The Day of Firstfruits is an Old Testament feast in which a sheaf of first grain was shaken on the second day of the Sabbath.
In the New Testament, it became the firstfruits of those who have fallen asleep and changed to Resurrection Day commemorating the resurrected Jesus.
Since Jesus was killed on the cross, the disciples of the Church of God were in shock and sorrow. However, they regained faith and the power of the Holy Spirit through Jesus' resurrection and planted a living hope for resurrection in many people.
The reason why we can smile even in the harshness of life is that the resurrection of Jesus has become the hope of salvation for mankind who are caught up in death, giving them the certainty that they will be transformed into angels and go to heaven in the future.