Working hard to lose

How do you cope with this?
I get it's somewhat of a vague topic but it can cover a lot of things such as going through college only to be denied the career you wanted, working a job for a year only to be sued by them for more than you even made, helping someone only to have them screw you over, etc.
I'm sure everybody has these things happen to them at times. Some more or less than others.
I get the only thing to do is to move on.
But how do you cope with that when it keeps happening.
What do you do when you tried the "it will get better" attitude long ago and even then had been fighting against loss with a positive attitude for a long time.
Optimism seems to be the only positive answer and people will say that if you are negative, negative will happen, so there is no other choice than to be optimistic.
Is there a limit to that optimism? Obviously some people go their whole life trying and working as hard as they can only to have the worst happen. It is inevitable that some will lose and some of those will be the hardest workers.
How do you deal with getting kicked when you're down repeatedly and optimism is shown to be delusion only to have others add the insult to injury saying you're not trying, or being negative?
It's important to never give up and move on but sometimes there seems to be a limit to that energy. How do people deal with this?