Praying helps us offer our concerns and worries to God, shows compassion for others and comforts us in our dark moments.
The longing for happiness, deeply rooted in the human heart, has always been accompanied by a desire to be freed from illness and to be able to understand the meaning of sickness when it is experienced. This is a human phenomenon, which in some way concerns every person and finds particular resonance in the Church, where sickness is understood as a means of union with Christ and of spiritual purification. Moreover, for those who find themselves in the presence of a sick person, it is an occasion for the exercise of charity. But this is not all, because sickness, like other forms of human suffering, is a privileged moment for prayer, whether asking for grace, or for the ability to accept sickness in a spirit of faith and conformity to God's will, or also for asking for healing.
– from The Congregation for the Doctrine of Faith, Instructions on Prayers for Healing