Leaving anything that you have made a habit of devoting your time to can be difficult. A good church is supposed to be an extended family, so leaving will naturally trigger different emotions. Telling your pastor that you are leaving the church must be a difficult part of moving on, but by handling it appropriately, you will feel more at peace to begin the next chapter of your life.
Define clearly in your mind the reasons why you are leaving. If they are purely circumstantial, be clear about why the situation led to your decision. If you are leaving due to a conflict or disagreement, try to detach from strong emotion and objectively define for yourself the specific issues.
Arrange a meeting with your pastor. You could also write a letter if there are personal reasons preventing an in-person conversation.
Discuss your situation with your pastor, clearly outlining for him the reasons why you are choosing to leave.
Thank your pastor for the time he has spent with you.
If leaving on good terms, ask for your pastor's blessing in the next part of your life.