Do we realise "Full stops"?

I really have a weird thought today. Can we realise that there is a "full stop" in a particular thing. Nice moral stories may go on and on about how efforts can change fortune and blah blah. Well wake up in actual world it does not happen. In actual world things end and efforts are lost in thin air. That accepted and acknowledged can we know when to "stop", know that our efforts further will yeild nothing as such. I am generally very optimisitc person, I always hope that things do really happen for good and that even the worst possible dark cloud has a silver lining. I have a strong sense of hope and always hope for the best in whatever is left. Still sometimes I just have a feeling that something is just "done"..gone finished, fertig. Generally seeing the probablity of 50% the probablity of it happening is suprisingly accurate. So can we generally know that our efforts are going to go down the drain?
Even in relationships and frienships can we realise the "point-of-no-return"? can we realise that a certain relationship is battered beyond repair and just move on with our life? It may be very difficult for normal people but when you are an astrologer you sort of develop a detachment from the materialistic world. We astrologers tend to see the world and its people, their miseries in third person and slowly slowly we start looking at family,friends and lastly self in a perspective of a third person. So we can actually detect a dead end??