I think the best i can expain it is that "soy" is to speak about what i'm ,like. Soy gordo, flaco, profesor, mexicano, rico, pobre. I'm fat, slim, a teacher, mexican, rich, poor. On the other hand, "estoy" is used, when you're talking about how and where you are. Estoy gordo, flaco, en México, feliz. I'm fat, slim, in Mexico, thirsty. You can use "soy" and "estoy" with fat and slim, because in both cases is what you are and how you are, but for teacher, well, what you are is a teacher, but it's not who you are neither where you are, Mexico is where and thirsty is how. I think that most of feelings can be used with both, but have different meanings. Soy feliz(correcto) (like i'm happy with my life) Estoy feliz(correcto)(like i'm very happy at this moment) "Estoy" is for HOW you feel right now Soy triste(correcto) estoy triste(correcto) Those are some example, but try to think "soy" is for "what" you are and "estoy" is for "how, where" you are and how do you feel. Saludos.

First of all, I’m not a teacher, but I am a Spanish native speaker and understand that “SOY” and “ESTOY” are very different and they cannot hardly never exchange. * You use “SOY”: - With a nationality: soy español, soy inglés, soy francés, soy chino, etc… - With a job or profession: soy médico, soy actor, soy fontanero, soy albañil, etc.. - With a personality adjective: soy egoísta, soy ambicioso, soy optimista, soy valiente, etc… (to describe yourself, your personality.) * You use “ESTOY” - With a place: estoy en el cine, estoy en casa, estoy en el trabajo, estoy en París, etc... - With a feeling adjective: estoy hambriento, estoy confuso, estoy mareado, estoy enamorado, etc… (to describe your feelings.) I hope I’ve helped you.

Eg. I'm here = Estoy aqui I'm tall = Yo soy alto. Estoy define el lugar donde estas, o definir como te sientes.... Soy es para dar adjetivos, o profesiones... Ejemplo: Soy: Yo soy profesor. Yo soy buena persona. Estoy: Yo estoy en Colombia Yo estoy cansado. Yo estoy joven = Yo soy joven; En este caso se podria usar soy y estoy.