PRINCIPAL CAUSE

The principal cause of suffering is impermanence, or transitoriness (annica).  Everything in existence is in a state of flux, changing, ever changing. The Pali word "anicca" literally means "inconstant." 

Impermanence has implications.  For instance, we identify with our empirical or egoic self, saying that this is "me," "mine," "my story."  "I am this one thing."  But since all is transient, there is no such "one thing" as this.  There is no permanent, unchanging, substantial, undeniable self. The Buddhist term for this is anatta, no-self.  A socially-conditioned, relative, temporary self exists, but this is all. 

This is frustrating because, to state a further implication, the person we remember ourselves to be is not the same person who exists in the present moment.  We recall feeling a certain way, happy, sad, angry, etc., back in high school, for instance, but the recollection is meaningless now.  This is to say, when we are happy, sad, angry, etc. now, it is not the same happy, sad, angry, etc. that we experienced back then.  This devalues our memories. 

In the same way, we cannot relate to ourselves in the future, anticipating, for example, how we will feel when we finally retire.  Again, we might be happy, we might be sad, we might be angry, etc., but there's no way to know.

It is all like grabbing a handful of water.  It just runs away.