Why are some Christians spiritually stronger than others?

People who aren't properly motivated don't tend to change. But when they are, they do. If you don't develop spiritual muscle, not only will you suffer, but people you care about might suffer as well. This sermon (also released as a podcast episode) explores the disciples' failure to help a severely demonized boy in Mark 9:14-32. Spiritual conditioning makes a difference, both then and now.