Everything is subject to change and dissolution, and people do not fully realise this - everyone feels things should continue in a consistent and predictable way, exactly as they themselves predict. People are sad when pleasant things stop, and if things are unpleasant, they are sad until they stop.
The way to remain happy despite all this change is to have Right View.
Right view is the understanding of the Four Noble Truths about suffering, its origin, its ceasing, and how to let it cease.
The four noble truths have three rounds & twelve permutations.
The Four Noble Truths are:
1. ~ The Truth of Suffering (i.e. that there is suffering) - there are many kinds of suffering, for example pain, ageing, sickness and death, association with the unwished-for, separation from what is loved.
2. ~ The Truth of the Origin of suffering: the cause of suffering is just this: craving for pleasures, craving for existence, or craving for non-existence. The Gates through which these causes dissolve are: The Signless, The Wishless, and Emptiness.
Turn the wheel? ...
Right View is the first step of the Eightfold Path, and it leads to happiness because one first of all realises that there is suffering, and then can see more about where it comes from, and that something can be done about it, and this enables one to be interested in knowing how to extinguish suffering and therefore to want to follow the path.
There are many ways of seeing with Right View:
To understand what is wholesome and what is unwholesome,
to understand the causes and rounds of nutriment (physical or mental),
to understand the four noble truths about suffering, to understand
any of the 12 parts of dependent origination (the arising and ceasing
of birth, or ageing and death, or being or craving or clinging,
or feeling or contact, or the sixfold-sense base or that which apprehends
it, or consciousness or ignorance or the will to know), or lastly
to understand the origin and cessation of the three taints, which
are the taint of ignorance, the taint of being , and the taint of
desiring to sense pleasant things.