This is from my book, Declarations. Reason #27 out of 30 for why we make declarations.
The making of declarations is one of most practical ways to renew our minds and implement Romans 12:2 in our lives – "And do not be conformed to this world, but be transformed by the renewing of your mind" (Roman 12:2). The renewing of the mind does not happen by osmosis, but by an intentional plan to dismantle wrong beliefs and establish positive strongholds in specific areas of our lives. Besides meditating on scripture, there is probably no greater strategic step we can take to renew our minds than declarations. It is an irrefutable law of the spirit that if we renew our minds, we will be transformed. It will work for everyone no matter what our past has been. Truly, nobody's past can limit their future, but current beliefs can. Declarations help us renew our minds so our lives will be truly transformed. "Faith comes by hearing" (Romans 10:17), and we get to determine how much we hear by how much we declare.