With a blown-up engine, changing the oil isn’t going to reassemble it magically. Similarly, depression won’t go away by meditation.
Prevention is better than cure, obviously. The danger lies in prevention advice being passed around, disguised as cure advice. They’re unequivocally not the same.
Maintenance is, of course, an excellent strategy. Meditation or prayer, among other initiatives, can help keep you grounded, focused, and grateful. Think of it as the oil recommended by your car manufacturer (not the cheap knockoff either). Proper and regular servicing will make you run smoothly for as long as you can.