Soy not estoy?

Question

Why is it soy cinturón verde and not estoy cinturón verde?  as being a green belt wouldn't be a permanent position.

Answer

I thought the same thing.

Answer

Hola Nina y Chrsitine
Interesting question!! 
To be honest there is no straight forward answer to justify the use of "ser" here. I can only say that I see this as "description" in a similar way to when we describe our personality or we say what we do for a living: Soy estudiante, soy una excelente profesora,... - the fact that these may be temporary states doesn't matter so much. This, for me, is talking about identity. You are identifying yourself somehow, the same way we do with professions. 
Soy estudiante. Soy profesora. Soy cinturón verde. Soy la ganadora del concurso. 
This is all giving some kind of identity to a person. 
I hope it makes sense. 
Saludos
Inma

Answer

Thank you.  I can understand the reasoning behind that. :-)

Answer

I gave up using “permanence” as a guide the moment I came across “está muerto” !  Now I use “identity” and “state”.