The gift of "praying in the Spirit" or the gift of tongues is the least of the gifts but the one that causes the most difficulty for people. There are many things we would do differently if we were God, but the fact is this gift is a true gift from God. It is also referred to as the language of angels and children. 

This is how St. Paul speaks about it in his Letter to the Romans: "The Spirit too comes to the aid of our weakness; for we do not know how to pray as we ought, but the Spirit itself intercedes with inexpressible groanings. And the one who searches hearts knows what is the intention of the Spirit, because it intercedes for the holy ones according to God’s will." (8:26-27)

Trusting in the Lord, we are called to yield our voice so that the Spirit can pray to the Father in what  may sound like childish babbling, but in reality is a prayer of praise to the Father.

Again, Paul's teaching on the subject. " For one who speaks in a tongue does not speak to human beings but to God, for no one listens; he utters mysteries in spirit. On the other hand, one who prophesies does speak to human beings, for their building up encouragement, and solace. Whoever speaks in a tongue builds himself up, but whoever prophesies builds up the church.Now I should like all of you to speak in tongues, but even more to prophesy. " (1 Cor 14:2-5)
And the one who searches hearts knows what is the intention of the Spirit, because it intercedes for the holy ones according to God’s will.2And the one who searches hearts knows what is the intention of the Spirit, because it intercedes for the holy ones according to God’s will.