"Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered." (Romans 8: 26)
Our prayers in our efforts are self-centered by their origin.
On the day of Pentecost, God provided a way for His glory to be fully manifested to the Jews on that blessed day:
"And when the day of Pentecost was fully come, they were all with one accord in one place. 2And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. 3And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. 4And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance." (Acts 2: 1-4)
Praying in the Spirit, or praying in an unknown tongue, allows the Spirit of God to speak through us, without our flesh (our mind and feelings) getting in the way.
God has provided us this better way to pray, one which is always in line with God's will, and edifies our entire man:
"He that speaketh in an unknown tongue edifieth himself; but he that prophesieth edifieth the church." (1 Corinthians 14: 4)
Who is the Holy Spirit, and what does He do for us? The Amplified Translation brings out the full extended ministry of Him in us:
"But when the Comforter (Counselor, Helper, Advocate, Intercessor, Strengthener, Standby) comes, Whom I will send to you from the Father, the Spirit of Truth Who comes (proceeds) from the Father, He [Himself] will testify regarding Me." (John 15: 27, AMP)
He is our advocate within us revealing to us what Jesus does for us at the right hand of God the Father today:
"33Who shall lay any thing to the charge of God's elect? It is God that justifieth. 34Who is he that condemneth? It is Christ that died, yea rather, that is risen again, who is even at the right hand of God, who also maketh intercession for us." (Romans 8: 33-34)
This Spirit within us intercedes on our behalf, first of all convicts us of our righteous standing before God in Christ:
"8And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: 9Of sin, because they believe not on me; 10Of righteousness, because I go to my Father, and ye see me no more; 11Of judgment, because the prince of this world is judged." (John 16: 8-11)
He teaches us all things, too (1 John 2: 20, 27) and informs us of our new identity as adopted children of God (Romans 8: 15; Galatians 4: 6)
Most importantly, though, when we pray in the Spirit, we found ourselves kept, guarded by the love of God:
"But ye, beloved, building up yourselves on your most holy faith, praying in the Holy Ghost," (Jude 20)
Intercession, protection, and affirmation: the Spirit is praying for us for all things!