As you (Natas) state, once the Intention is cast, it should be thought of no more. According to Paul Foster Case, and clear reasoning, the reason for this is simple psychology. Manifestation arises from internal belief, "As a man thinketh, so he is."
Repeating a desire indicates to your inner self that there is a lack. Therefore, this belief becomes your reality!
It is written, " Therefore I say unto you, What things soever ye desire, when ye pray, believe that ye receive them, and ye shall have them." - Mark 11:24 KJV.
It is clear from this that the proper manner for attainment is to express Gratitude for what you already have. In order for this to work, you must believe that every good thing is already yours, freely given by the Bestower of all things. Since the Self-Aware Power That Is, Was, and Shall Be exists beyond the confines of Time and Space, the Eternal Now, so do your "blessings".
It's like a brand new car with title, keys, and a full tax of gas is sitting in the street awaiting you to get in and take possession of it.
How many would simply walk on by assuming that it belongs to someone else because they can't be, or aren't (in their innermost mind), worthy of owning such a thing?
The Word informs us that every good thing has been created expressly for us. Believe it and receive it!