There is an enormous power in verbally expressing what you believe. Notice Jesus did not instruct us to think about what we want God to do, but rather to declare it for ourselves. It is imperative that we speak what we believe. If we do not, we allow doubt to creep in and destroy our faith.
I have talked to many people who are disappointed that they don’t receive what they pray for from God. Yet, almost without exception, I find that they do not believe in the power of their own words. Don’t let fear hold you back; speak out and claim the miracle you need.