https://liveanddare. com/contemplative-prayer-and-christian-meditation/
This is a nice article that goes over Christian meditation.
For Christian anons, this is a great tool that has helped me through many years.
When you are feeling depressed, just recite the Aramaic word "Maranatha" which means "Come Lord" or "Lord is Here"
Whenever attention wanders on the negative or you find yourself ruminating, just recite the mantra like how you would gently pet a cat. And say it with intention in your mind towards the good, towards Christ, God. And when the mind wanders, just bring it back to the word.