I have harbored such thoughts before.
What has worked for me in the past, is reflecting on how absurd the motive for such a drastic action usually is.
For example: A co-worker (who has been having a midlife crisis) came to work with a 'rare' flavor of energy drink. (Not regionally available, but strongly preferred) A resident that does not respect the boundaries of other people's things took it while we were both engaged in rooms, opened it, and drank it. This was the final straw for my co-worker, who went off the rails, and actually hurt herself in a fit of rage over the incident. (Again, this is the result of a final straw type situation, not indicative of normal behavior.) She was discussing her desire to make this shit stop by ODing on her insulin.
Now-- Think about it rationally; A 2$ energy drink is the final motivation for such an action? Really? Isn't that just a bit absurd? When we reach our emotional coping limits, we reach the end of our coping limits, so explosive results are expected, not unreasonable. What is unreasonable is that we get pushed into such situations in the first place, and end up resorting to "final solution" thoughts or deeds over things that normally we would consider just plain stupid.
Being able to stop, reflect on that, and go "yeah, that's absurd." has been a major rallying ability for myself more than once, since it follows with "What's more absurd, is that I have gotten to this point by allowing (list of stressors) to get me here."
I know it can be hard to muster that level of rational clarity in the depths of emotional chaos, (from personal experience), but doing so is very helpful, and a source of great strength to change your position.