One of the most important tasks you have as a missionary is reactivation. In many cases, reactivation can be even harder than making a new convert. To help reactivate someone, you need to understand them.
John P. Dehlin, founder of Mormon Stories, was a strong missionary and a strong member, but went inactive because he just couldn’t reconcile with certain aspects of church history and doctrine. While he was away, he ran into a lot of members who didn’t understand why he left, assuming that it was out of laziness or because he wanted to sin.
He’s since returned to church and has put together a great video about why Mormons leave, using data from a survey conducted by over 3,000 former members of the church. It’s very eye-opening and will help you better handle those who’ve left the church.