It's more of a prevention than a cure, but Stoicism (the philosophy, not the abstract concept) is a good philosophy of life that would help strengthen you for this kind of negatives. You wouldn't stop caring or feeling, but you'd be more in control over what the feelings do to you, and see these events in a more "positive" light.
I'll note that you probably mean this in the original sense of Zeno's philosophy and not the modern use, which has more of a connotation of emotional repression. Somewhere along the way from ancient Greece "stoic" began to mistake the original's sense of not allowing yourself to be controlled by your emotions to something like not experiencing them to begin with. Though to be fair, even the original held that certain things like fear were not rational and fully developed stoics wouldn't experience it, and in general that emotional extremes were to be avoided.
In some ways it is very like Zen Buddhism in this sense of accepting things as they come without being rule by them. (The naming is only very coincidentally similar-- Zeno's stoicism and Zen)
I recommend "A Guide to the Good Life" by William Irvine. The title is a bit off-putting, but it gives a good survey of the philosophy and history of stoicism along with good examples of applying it to modern life. After reading it, you might have a better sense of which primary sources will be most relevant to what you're looking for.
Little to none of his work has survived intact, so what we know is mostly through other people. IIRC, a lot comes from Seneca and Marcus Aurelius's auto biography "meditations". Searching around on Seneca, his letters on the topic have been collected in a book "Letters from a Stoic"
