Peoples' lives can vary - for example one may have a great experience of work, marriage or health, while someone else's life experiences are fraught with difficulties. We comfort ourselves saying 'everyone has problems' - which is true, but I believe some people face more challenges than others*. Like a child, we may protest "it's not fair!"
Justice is another story. While I'm not sure life is fair, there seems little doubt that justice is impartial. During this lifetime, we may not always get what we deserve for harm done, but down the road a penalty will be due. Will we accept Jesus' payment of our penalty, and enjoy mercy, or will we pay for it ourselves?
*But Abraham replied, ‘Son, remember that in your lifetime you received your good things, while Lazarus received bad things, ...' (Luke 16:25a NIV)