Stoicism is an ancient philosophy, which came back into the public view in personal development circles. Stoicism aims to be light on theory and uncomplicated to apply, though probably not easy.
The philosophy touches on many topics, but it bases most of it's thinking from the idea that you should live your life as so to maximize the very best qualities.
You shouldn't think of an event as terrible and unfortunate, or great and you're lucky for it to have happened. Instead, you should be indifferent, as such extreme emotional reaction has caused many to go to ruin.
And while you aim to remain level-headed no matter the situation, you can attach preferences to indifferent situations regardless - with the term 'preferred indifferent' and 'dispreffered indifferent'. You can have opinions that an event would be better if it had happened, but you should only prefer the event, not desire it immensely.
In The Obstacle is The Way by Ryan Holiday, a book on stoic thinking, Holiday describes the benefits of emotionally disengaging from setbacks and failiures. Stoicism posits that since displaying the greatest virtues at all time should be our goal, any great misfortune is an opportunity to display courage, level-headedness, and to prove our mettle.
A disaster on it's own is bad enough, but a disaster and you loosing your composure is far worse.