Who says you can't pray in your own words? G-d is always ready to listen
to the prayers of a Jew, regardless of his choice of words or language.
It is well-known that many of the early Chassidic masters supplemented
the daily services with personal prayers in Yiddish. According to Maimonides
[Laws of Prayer 1:5], we fulfill our Torah-obligation to pray by simply
asking G-d for our needs once a day. Nevertheless, you miss out on something
special if you do not say the prayers in the siddur.
Jewish prayer today is based on the offerings that were offered in
the Holy Temple. While the spontaneous prayers of an individual correspond
to the large variety of offerings which anyone could bring at any time,
the fixed prayers in the siddur, which are for all Jews to say, are
in place of the obligatory communal offerings. Tefillah [prayer]
literally denotes "connecting," and reporting in on a regular
basis is an important component of this.
The Jewish sages of the Second Temple period, paragons of spiritual
sensitivity, understood well the "language of the soul." Divinely
inspired, they standardized the daily prayers, using precise, powerful,
mystically attuned combinations of letters and words. Saying these prayers
is always beneficial, even though we may not be able to perceive it.
Of course, it is even better to understand the words and, even more
important, to be sincere. This is why many people who don't know Hebrew
choose to pray in the language which they are most fluent. Even in such
a situation, however, it is preferable to say at least the first two
lines of the Sh'ma and the first paragraph of the Amidah in Hebrew,
since they are so important. A word of caution: those that pray in English
should avoid those siddurs that do not print G-d's name in English but
instead use the substitution, "Hashem."
The sages also provided guidelines for adding personal prayers to the
fixed prayers. There are specific places for inserting prayers on specific
subjects, but any prayer can be added just before taking the three steps
backwards at the conclusion of the Amidah.
To sum up, both types of tefillah are recommended: the fixed-prayer
offerings (e.g., Sh'ma and the Amidah) to enable one to
connect with G-d as part of the Jewish community, and spontaneous prayer
in whatever language, to develop a more personal relationship with G-d.
[Part of this question-answer is from ASCENT QUARTERLY
#1 (Fall 1983), and part from ASCENT QUARTERLY #18 (Spring 1990).]