So how does the "letting them go" approach differ from the simply being civil and not initiate contact or prolonging contact method?
When you simply go dark you prolong limbo. You still spend your time thinking about what the WAS is doing/thinking/feeling. You're just maintaining the status quo and therefore the WAS can also to continue to cake-eat. Why would they ever make a choice if they don't have to?
When you set them free, you also set yourself free. You make a decision to reclaim control over your own life. You move in a new direction, one that is solely what you think is best for yourself. Then your WAS will have to make a choice--you or the other life--because it is no longer possible to have both.
If you love somebody, set them free. http://tinyurl.com/2empx2g