I appreciated these thoughts from Tim Spivey on the issue of churches losing members:
Generally, unhealthy people leave healthy churches and healthy people leave unhealthy churches. The question is, "Who are we losing?" No matter how great a church is, people will leave that church—through moving, attrition, or other causes. The question isn't, "Will we lose people," it's, "Who are we losing?" If you are losing people who are heretics, critical, gossipers, divisive, or unwilling to behave Christianly…that's a sign of health. If you are consistently losing people who are truly salt of the earth, or entire age groups…you should really pay attention.