It's said that the only certainties in life are death and taxes; I would contest we add uncertainty to that list as well. For all the steps we take planning and preparing in our lives, we inevitably take detours into the land of uncertainty.
I would say that the most apt, and humourous, description of how humans deal with uncertainty I have been witness to was delivered by Tony Robbins. During his Unleash the Power Within seminar in November, 2016, he posited that humans are perfectly accepting of uncertainty -- until that uncertainty becomes uncomfortable or unwanted; at that point, we refer to the uncertainty as 'problems'.
Consider this: you find a stray $10 bill on the ground; your table receives a free appetizer at a restaurant, compliments of the chef; a hotel double-booked your room, and upgrades you to a suite. Most of us would more-than-welcome any of these uncertain scenarios, largely because they benefit (or at least do not harm) us. Conversely: we lose a $10 bill somewhere between the house and work; your favourite meal cannot be made because the restaurant is out of the key ingredient; the hotel that double-booked your room turns you away because they are over-booked. These scenarios, while also uncertain, generally would be referred to as 'problems', and not looked upon with the same optimism as the original three.
So many people focus their attention on the negative outcomes of any given scenario, meticulously attempting to hedge themselves against uncertainty; this is not only limiting to beliefs (by only focusing on the negative) and actions (by restricting what you do / don't do), but can lead to tremendous stress and anxiety. If we can learn to live with uncertainty, shifting our focus from attempting to avoid bad things that might happen to accepting the unknown as a possibility, we shed a terrible weight we put on ourselves. We can still make plans, schedule, and prepare -- but understand and accept that the unknown will occur at the same time.
I am by no means suggesting we take a happy-go-lucky approach to life, glibly smiling as unfortunate circumstances happen to us. Rather, I implore that we recognize uncertainty as something we will encounter in our lives and embrace it. After all, if we don't treat every 'good' uncertainty that comes along as the best thing to happen in our lives, we should really try not to treat every 'bad' uncertainty as the worst thing -- it's all about balance.