I asked a friend who is a meditator about my practice of compassion, and he suggested I do breathing meditation because it helps liberate the mind from overthinking, as well as relaxes the person. However, I'm slightly skeptical because metta typically is also considered a concentrative meditation. Wouldn't compassion meditation also relax the mind because of this?
Thank you
Someone practising metta meditation can make one's mind concentrated easily but metta meditation does not in itself result in deep absorption as the object of concentration is changing and vittaka vicara is needed think "so and so be happy", etc.
Breath meditation, on the other hand, helps develop concentration and studies ones mind from overthinking.
Breath meditation with a bit of metta meditation will help deepen the concentration.
According to at least the Visudhimagga (chapter 9), you can reach jhana when practicing the Brahmaviharas of which compassion is one. Yeah, good luck with that. Practically speaking, it is far, far more difficult to develop concentration to the point of absorption when using a complex, abstract concept as the object of meditation. The mind is just too easily given to vacillation. In a Brahmavihara meditation, you are imagining people, their mental state, your feelings for them, and so forth. There's a ton of potentially moving parts. Samatha meditation requires stability. Think of dropping a hunk of uncooked meat on a table. Hear that slap, feel the weight of it, see that piece of roast beef kinda relax as it settles. It ain't going anywhere. Your attention has to drop on it's object in much the same way (at least initially...eventually you ease up on the gravity). You can do that with compassion meditation, but man, if you're looking to develop the same amount of relaxation and absorption as say, breath medtiation, you are setting yourself up for a pretty rough go of things.
Wouldn't compassion meditation also relax the mind because of this?
Yes. Absolutely.
If you could meditate about walking to the gallows after being unjustly convicted and do so spreading a heart full of love, compassion, rejoicing and equanimity limitless in all directions, then your metta meditation is rock solid and well developed.
That would be the painful practice with swift insight discussed in AN4.163:
And what’s the painful practice with swift insight? It’s when a mendicant meditates observing the ugliness of the body, perceives the repulsiveness of food, perceives dissatisfaction with the whole world, observes the impermanence of all conditions, and has well established the perception of their own death.
You might prefer instead the pleasant practice with swift insight meditating on the breath:
And what’s the pleasant practice with swift insight? It’s when a mendicant … enters and remains in the first absorption … second absorption … third absorption … fourth absorption …
Both are effective.