Who we are can be divided many ways, but one way to look at ourselves is as spirit and vessel. Our spirit is that special, immaterial part of us that communes with God, and our vessel is our physical package of mind and body. In normal cases, it is our mind that controls our vessel. Our mind gives the commands, and our body follows. But when speaking in tongues, it is totally different.
Paul describes what happens by saying, "For if I pray in a tongue, my spirit prays, but my understanding is unfruitful" (1 Cor 14.14). When praying in tongues, my spirit is communing with God outside of the control of my mind, outside of my understanding. My mind has nothing to do with this communication. In fact, when one tries by the strength of the mind to control what is happening, that is when the communication is lost.
But then, what is your body's part in this? The part of praying and worshiping in tongues that people can see and hear is the words you are speaking our loud. It is easy to confuse the sounds coming out with the actual spiritual communication, but they are distinct. My brother once described the physical manifestation of tongues (your mouth speaking) as the Spirit "throwing your vessel a bone" while the real communication is happening inside. I have to agree.
Speaking in tongues is a deep, spiritual experience and happens on the inside. God is not waiting to hear what you say on the outside! What is important is what is happening on the inside. With this in mind, one realizes that the actual sounds they are making do not even need to be perfect. The reality is that when we focus on the sounds we are making, we end up hijacking the experience with our minds!
My point in this section is that you do not need to feel silly or foolish because of the strange sounds that are coming out of your mouth. You just need to understand by faith that you are communicating via your spirit, not your mouth, and just let your vessel go with the flow.
The more you commune this way, the more you will learn to separate your mind from what your body is doing. The farther your mind is from the process, the better and more intense it is! As I mentioned in an earlier section, I find that praying in tongues is a great time for thought and meditation. With your body connected directly to your spirit, your mind is completely free. As my mind drifts through thoughts of life, God and scripture, I find clarity that is not available to me in normal cases.
I write all this to say that you must understand the distinction of your spirit from your mind, and learn to separate your mind from what the Spirit is doing through your vessel. But this all becomes easier as you grow in the gift through faith and practice.