As any good writer, speaker, teacher, and actor knows, every word we utter — and every gesture we make — touches off something conscious or unconscious in our listeners. After all, each word has an outright meaning as well as a world of undertones and implications; and both are fecund with implications that always leave their mark.
Now, that’s also true when we pray. Everything we say is “taken in”, and things or circumstances are affected accordingly — whether we know it or not. But just as your words have a greater impact upon someone you’re very familiar with than on someone you’re not, that’s also true of your prayers. The closer to G-d you are and the more familiar you are with Him, the greater the impression your words leave with Him.
Knowing all that, our sages set out to formulate prayers that would foster the sort of effects that needed to come about. And they also encouraged us to draw as close to G-d in prayer as we can. That explains the hidden import of the words we use in formal prayer and all their practical halachic details and requirements.