'There is nothing either good or bad, but thinking makes it so.'' the quote is taken from Shakespear's play -

Some important quotation from Shakespeare's Hamlet:
- Brevity is the soul of wit.
- Listen to many, speak to a few.
- There is nothing either good or bad, but thinking makes it so.
- To be or not to be that is the question.
- Frailty, thy name is woman.
- Neither a borrower nor a lender be; For loan off loses both itself and friend.

Source: Hamlet, William Shakespeare & The Oxford Dictionary of Quotations