Rebbe Nachman of Breslov zt”l once spoke to a youth and encouraged him to seclude himself and converse with God in his native language. The Rebbe told him that this is how prayer began. The main form of prayer was an expression of the heart before God in each man’s native tongue.
Rambam speaks of this in the beginning of his code on prayer (Yad Chazakah, Tefillah 1:2-4). He states that this was the main form of payer in the beginning, before it was formalized by the men of the Great Assembly. It was only then that a formal order of payer was introduced. But even according to the Law, the original form is still foremost. Even though we follow the order of prayer ordained by the Great Assembly, the original form is still most beneficial.
Make a habit of praying before God from the depths of your heart. Use whatever language you know best. Ask God to make you worthy of truly serving Him. This is the essence of prayer… This is the way all the Tzadkim attained their high level. ~ R’ Noson of Breslov zt”l