Buddha says all sanskars are annicca. If harmony is a sanskar then disharmony is waiting to happen. Therefore my question is are we waiting for disaster to happen ?
There are three types of emotions, pleasant, unpleasant and neutral. Just like everything else, they are impermanent/anicca, as you already have stated.
When we attach (upadana) to pleasant emotions we create unwholesome karma, since pleasure/sukha becomes dukkha/unsatisfaction as soon as it ceases. So yes, clinging to harmony means "waiting for a disaster" as you put it.
Looking at the four noble truths, the above is covered in the first two truths regarding dukkha and samudaya (how unsatisfaction arises). There are also the truths about nirodha (cessation of dukkha) and magga, telling us that dukkha can end with the right means. The point is that there's more to life than just waiting for a disaster.
If you ask me, harmony and chaos are just arbitrary labels the mind uses to evaluate things based on some also arbitrary criteria. By understading the conventionality of such concepts, and by understanding where do they come from (the mind, preferences, attachments and points of view), harmony and chaos stop being some objective measures of reality, and they are seen for what they are: arbitrary assessments arising from the proliferations of the ignorant mind, imposing its judgements and expectations into the outside world.
So, I'd say that disaster is on the eye of the beholder.
Not because something goes against ones desires and expectations, does it mean it deserves to be labeled as "objectively" and inherently chaotic or disastrous. It all depends on your definitions of those words. To define, you need some criteria; but language, as a conventional tool used for practical purposes, requieres to assume that we all agree on such criteria. Why is death more disastrous than life? I think all we can say is that when ignorance and craving are present, dukkha arises; everything else are just subjective points of view.
In sum, I'd say that we suffer because we expect things from the world that go against how things truly work: all conditioned things behave according to the three marks of conditioned phenomena: things are impermanent, not-self and do not lead to complete and utter satisfaction.
And so, I'd say disaster is on the mind of the one expecting states and results ignoring these three marks of conditioned phenomena.
I imagine that "harmony"" and "disharmony" are opposite extremes. That seems to me to be the sort of "dual" about which the Buddha said,
Avoiding these two extremes, the Realized One teaches by the middle way:
‘Ignorance is a condition for choices. Choices are a condition for consciousness. … That is how this entire mass of suffering originates. When ignorance fades away and ceases with nothing left over, choices cease.
There the word "choices" is a translation of saṅkhāra.
The word saṅkhāra seems to have a wide range of meaning -- Can anyone explain Sanskara / Sankara indepth?