Some applicants may ramble on about themselves in a manner that may appear self-indulgent and not very appealing to the committee. Remember, this is an application essay, not an autobiography. Conversely, some applicants tend to say too little, perhaps hesitating to promote themselves too explicitly or not knowing what about themselves would be interesting to people whom they don't know. In such cases, perhaps focusing more on what you want to do than on what you have already done (let your record speak for itself) may help in getting beyond self-inhibition.
Sorting out the Christian essay topics is a laborious and time consuming process, as you have to become familiar with specific terms and historic events described in the Bible in order to understand what you are writing about. Try to select one of the Christian essay topics that you are familiar with to some extent, so you can handle it. Choose a topic that has kind of a hook and not only relates to Christianity, but also is of interest to you, as working with something that is interesting gives better results and makes the process of working more enjoyable.