I wish I was or I wish I were... please help
Russian English teachers commonly says that in the structure "I wish I was (were)" we should use "were". But when I watched "Forrest Gump" and "The Game of Thrones" I had heard:
1. Forrest says: "I wish I was the shoes like that"
2. Tyrion says: I wish I was the monster you think I am"

how is correctly? :) and why?

Question

I wish I was or I wish I were... please help
Russian English teachers  commonly says that in the structure "I wish I was (were)" we should use "were". But when I watched "Forrest Gump" and  "The Game of Thrones" I had heard: 
 1. Forrest says: "I wish I was the shoes like that"
 2. Tyrion says: I wish I was the monster you think I am"

how is correctly? :) and why?

Answer

Technically, the proper structure is "I wish I were," as your teachers taught you.  However, it is a more formal sentence structure and many native speakers use "I wish I was" when they are speaking more informally.  That is why you heard it in films/tv shows.

Answer

"I wish I were" is the proper correct form because it is a wishful sentence (expressing something that is not true right now), and wishful sentences use the subjunctive form.

But "I wish I was" is SUPER common because we English speakers like to just make things easier for ourselves ;) haha.

For a detailed explanation, see this page on Grammar Girl (which is excellent by the way for explaining complicated English grammar rules): http://www.quickanddirtytips.com/education/grammar/subjunctive-verbs

Answer

I agree with Sarah.
My personal habit is to always say "I wish I were" but I'll hear "was" quite often.

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