This is just a well-known Christian hymn, but can have great power when you're in a dark place, and I've seen people making use of it to comfort and give strength to themselves when they were in some horrible situation or knew they were going to die.
The simplest and most known can be just effective as the more esoteric or Eastern style kinds, and I've found it can calm me down and get me out of dark places. Seems good for depression particularly. My impression is that it heals by inspirering a faith and trust in God's providence, but this is true for many of the old Christian hymns.
So just to get some of that out of the way:
The Lord is My Shepherd
The Lord is my shepherd, I shall not want
He makes me lie down in green pastures
He leads by the still waters
He restores my soul
He leads me down the paths of righteousness for his name's sake
Yea, even as I walk through the valley of the shadow of death
I will fear no evil because You Lord are with me
Your rod and your staff they comfort me and make me feel safe
You prepare a table before me in front of my enemies
You anoint my head with oil
My cup runneth over
Surely goodness and mercy shall follow me all the days of my life
And I will dwell in the house of the Lord for ever
And of course the famous prayer Jesus taught us never loses its power when used with sincerity:
Our Father
Our Father, who art in Heaven
Hallowed be Thy name
Thy Kingdom come
Thy will be done on Earth as it is in Heaven
Give us each day our daily bread
And forgive us our debts as we forgive our debtors
Lead us not into temptation
But deliver us from evil
For the Kingdom is Yours
And the power and glory
Forever
Just a few words about how I make use of these kind of prayers. What I don't do is just proclaim them once and expect for a miracle to happen like a child would. They have no value if they are just empty words, and there are many who just experience them as empty words if they haven't learned to use them as a means to reach higher levels of consciousness and receive beneficial energies.
They can actually be used as a kind of mantra. It's more like I go into a meditative or trance-like state where I meditate on the words as I repat them again and again until I start feeling some higher or healing form of energy. So pretty much like other forms of meditations, but I like to meditate on words.
I realise this isn't exactly what many have in mind for songs and mantras that can lead to spiritual upliftment, but don't completely ignore what is in your own backyard.