Be humble that you may receive God's grace and be raised up. Suffering is really for our benefit and is actually a gift - if we know how to use it. It may be as simple as saying a prayer and offering up our suffering to be united with Jesus's suffering on the cross. Suffering can be used as our purgatory on earth instead of having to go to purgatory later. Jesus, thank you for the gift of sharing with me your pain and suffering for the sins of the world.
Sacrifices work the same too.
Although sins are forgiven, they must still be made up for. For example, if a person breaks a window, they may be forgiven but they should try to make up for it somehow. Your suffering and sacrifices can be used in reparation for your sins or for the sins of others - either living or deceased. Mother Teresa explains too that suffering and sacrifices can be offered up to help others in their ministry or work. She would ask those who were suffering to offer their sufferings for the work of the Missionaries of Charity so that their offering would strengthen and make more fruitful their work.