Matthew 6:31 - "Therefore take no though, saying, What shall we eat? or, What shall we drink? or, Wherewithal shall we be clothed?"
In order to not take thought about one thing, one has to fill his thoughts with something else. In verse 31, Jesus gave us the basic key to controlling out thought lives. He said " take no thought - saying."
By putting a thought in our mouth and then speaking it, we take that thought. Once the thought becomes spoken words, it has been activated -- especially when a born again believer takes a thought and says it. We are the righteousness of God. We have the God given right to speak and expect.