I hope I was not misunderstood. Anyone can be mispallel for anything using their own words. That is not the issue. When it comes to authoring a tefilla to be “koveya” for others, then we are in a different ballpark. Here, there are issues of insuring that the tefilla is consistent with the dictates of halacha, kabala, etc., and that is a responsibility that comes with qualifications. I might aspire to achieve that level, but I have no reason to think that I have ever approached it. A personal tefilla does not need to qualify in any way, except to be the true emotion of the person saying it. In fact, the seforim speak much about those tefillos that are done by way of thought and meditation, not even put into the spoken word. As for the chosen language of a tefilla, one does not need language altogether, but one can rest assured that HKB”H understands us, regardless. The Kedushas Levi – R’ Levi Yitzchok of Berdichev noted that a parent always understands even the gibberish and mispronunciations of his/her child. So, too, HKB”H understands us, His children, without regard to our actual speech.
May HKB”H inspire all those who need to become closer to Him, children and their parents.