I think the depth of the message is in it's simplicity. I think you also know exactly what this message means. God is not mysterious. I guess I'd say the message means this....do not invest your self, do not feel guilt, do not expect anything for any further investment, further time spent is furthr time wasted. It sounds to me like you have been given permission to walk away from this person. As a matter of fact, it sounds like you are being commanded to walk away. In the spitual world, I believe "people" can be opportunities. God will not spend you on someone else. You were an opportunity that was taken for granted. Move on.