I will not pretend I have this mastered by I will say the best thing that I have done is discipline myself to separate the real from the unrealistic thoughts that fell all to real in my mind.

Classic example. I have king put suicidal thoughts to rest by reaffirming that despite the train wreck of a life I live there is still plenty of things worth living for! I realize that while the thoughts are very convincing that is not a realistic option.