Where do you draw the line?

In my line of duty, one of the 'unspoken' responsibilities is to 'save as many lives' as possible. Nope, we are not as noble as doctors, nor heroic as the firefighters and the policemen...but whenever we come across a 'lost soul', we do try as much as possible to put the person back on track.

But where do you draw the line?
When do you realise that no matter what you do, there are among those, who
a) take advantage 'second chances' too many times and abuse your trust and belief
b) simply can't be bothered to be saved
c) are so 'lost' beyond the point of redemption?

I don't know how to give an answer based on facts.  This is human nature...not some number game, or something that can be explained rationally or logically.
When I feel uncomfortable, and when I know the vibes and auras are not right...then I listen to my gut feeling.

Sadly...some people...there is just no point helping.
What a waste!