Is it ever possible to tell the purpose-driven purpose (in general sense) of a respected distressed disabled person?

I believe when a person is born God chooses him or her to carry out an action on this planet. And until that action is carried out they can never retreat from this world. Paralyzed people fully from head to toe who are like so from birth and those people in life who developed some intense illnesses that they never quite got over with and can't rebuild their lives or help their family, what was that purpose-driven life for them? I am asking this because I volunteer at an organization where broken people and people in wheelchairs come for help. I talk to them. I hear their distressing everyday life story. I want to know what was that God's chosen action that they have to carry out on this planet when they are so vulnerable themselves and are suffering so much? I also heard on tv that a pastor saying every person's life has a grand design. So this question.