Ser ser frequently refers to a permanent condition.
Estar estar often refers to a temporary condition
Use soy (the first-person present of ser)  to tell you what I am. 
Use estoy (the first-person present of estar)  to tell you what I am being. 

Estoy feliz I'm happy now.  Soy feliz I am happy by nature. 
Está callada she's being quiet. Es callada she's introverted.
Estoy listo I'm ready. Soy listo I'm  a quick thinker.
Estoy en Canada I am in Canada Soy de Argentina I am from Argentina.
Ser      Estar 
Aburrido boring   bored
Cansado  tiresome  tired
Divertido amusing   amused
Joven young  looks young
Viejo old  looks old
Listo  clever  ready
Seguro safe  sure
Vivo sharp/quick  alive
These two sentences can have different meanings in English. 
The apple is green. La manzana está verde condition temporary
(Meaning the apple is not ripe.)
The apple is green. La manzana es verde essence permanent
(Meaning the color of the apple is green.) 
In the first case, the example speaks of the condition of the apple.    
The apple is green because it has not yet ripened.
When the condition of the apple changes, that is, when it has ripened, it will no longer be green
In the second case, the example speaks of the essential characteristics of the apple  
The apple is green in color. 
This particular apple remains green even after it has ripened. 

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