The word Mantra is a composition of two Sanskrit root words: the first root being "man", means "continual or contant thinking". The second root "tra", means "free" or "to be free". Mantra is a process by which you free yourself from worries or doubts, but not from consciousness. Mantra is a means of transcending thought, and bringing consciousness to a much higher level of spiritual being. The root "tri" also means "to protect". In India, many mantras are called protective mantras.
A true mantra is one which frees you from constrictive limitations of mind thought. The whole meaning of practicing mantra is to find some degree of peace. When my thoughts are distracted during meditation, I begin chanting one of my favorite mantras, Om Nama Shiva Ya. Shiva is the divinity principle that dissolves away all imbalances. This mantra means "Oh Lord of Auspiciousness, to You my salutations again and yet again." It is a powerful mantra utilizied to experience God-consciousness.
Chanting a mantra calms down the mental chatter and allows me to connect more deeply to the spiritual experience, and myself. Although every mantra does have a word meaning, it is the feeling evoked within you, through the repetition of the mantra, that is meaningful. Mantra creates a stirring within your soul. It produces a spark. It acts as a catalyst to bring forth a stream of positive creative feelings, which will produce constructive thinking.