Everything changes, all the time. Constant movement is the signature of our universe, and our lives too: rhythmic change like the ebb and flow of tides, day and night, the seasons, and breath may give an illusion of constance, of reliability, but movement is what they are, so nothing stays the same.
Other changes are staccato and appear less predictable, like the stages of life cycles, weather patterns, human behaviour. For example, death, storms and rejection may appear suddenly and unexpectedly, yet they are all certainties.
To varying degrees, we all like sameness, conformity and predictability. Knowing what will happen next is one of our key requirements for contentment. The odd thing here is that we derive comfort even when the patterns that repeat themselves are unpleasant and unwanted. “I told you so”, and “I knew I was right” help perpetuate the myth of constancy. We place high value on people who ‘get it right’, even when ‘being right’ makes us unhappy.
In life, it is best to hold the illusion of certainty lightly. Adaptability is necessary for survival, and if that sounds a trifle sweeping or dramatic, consider that being light on our feet in the face of the unexpected is an attribute which has a direct effect of comfort and contentment. It helps us accept change, weather disappointment, and grasp opportunity.