Write a long, nasty, mean-spirited letter to explain everything that they dislike about the church and articulate their own self-pity at length. Entering into, engaging with, and departing from Christ's local body is a significant part of following Jesus.Keep your former church in your prayers and speak well of it. Church members should exercise graciousness and courtesy in leaving a church. Try to leave graciously. It's important to assess and communicate underlying issues biblically, accurately, and respectfully before leaving.