In Zen Buddhism there is not much use of mantras. We do have chanting, that includes some dharanis (a verse of supposed spiritual power) but they are generally confined to times of ceremony.
Tibetan Buddhism is different. There, mantras are used on a daily basis for all kinds of reasons such as connecting with a particular bodhisattva or Buddha, healing from illness and sending kindness and compassion into the world. Some people chant them near constantly, especially the universally popular Avalokiteshvara mantra ‘Om Mani Padme Hum’. Mantras are carved and painted into stone and left on the side of mountains, drawn on prayer flags and etched into large and small prayer wheels which are rotated to mechanically recite the mantra.
Despite an attraction to mystical ideas, I must admit I don’t generally buy into the idea of magic verses or words with innate spiritual power. Mantras have become useful to me by their association with certain images or feelings and also by their ability to calm the mind. This is where I use mantras most, especially during bad periods of illness or acute stress.
Mantras have been used for millennia in eastern meditation as a focus on which to meditate. The fact that the phrase had a spiritual meaning was believed to help and that has actually been confirmed by modern studies which demonstrate that people who were meditating could achieved a more concentrated state when they focused on words with a known spiritual meaning rather than more everyday phrases (as is typical, I am unable to find the exact citation but can assure you I did read it!).
The Sanskrit word mantra literally means ‘instrument of thought’ (from man to think and tra tool or instrument). I have also heard it translated as ‘mind protector’ but I am unsure of what entymology is offered for that. In any case, it rings true for me, as mind protection is the reason I use mantras.
During meditation, in Zen at least, we are taught to sit with an openness to all experience, both mental and sensory, and this is the attitude which we also try to take into life in general. When we are in pain or suffering stress, however, it is all too easy to fixate on that one thing. I am sure you have all had an experience of being overwhelmed with an anxiety about something – a test, job interview, medical results etc. Thoughts about the worry circle around in the head. Likewise, when we are in pain, it can be hard to distract attention from the place in the body which is hurting and constantly checking to see if it has worsened.
Opening up to these experiences, like we do in zazen (Zen meditation) can help to widen experience away from those things but sometimes it can be too hard. I experience this as an onrushing wave that I just cannot stand up to. My mind is swept away by it and cannot stay with the openness of experience. In this situation, I find mantras especially helpful. They act a bit like a mild analgesic to take the edge off of the pain just enough for it to be bearable, only in this case with our own experience. Reciting a mantra shuts out the endless repetition of the mind (I am sure you will have heard the finding that most of our thoughts have been thought before and that is probably even more true when we are cycling though worries about a particular situation or painful feeling) and allows a degree of calmness to be felt. I used a mantra when I was having blood taken just before the needle went in. Not a massively traumatic experience but still easier with a mantra. Others report using mantras at the dentist or during medical scans or examinations. When I am unable to sleep at night due to pain, mantras can be as useful as painkilling medication and at least worth trying beforehand.
So, the question is, which mantra should I recite? Well, that is entirely up to you. Through you spiritual practice you may have one already such as Om Mani Padme Hum. For those who are sick, the Tibetan Medicine Buddha mantra may be appealing:
Tayata Om Bekanze Bekanze Maha Bekanze Radza Samudgate Soha (click for audio)
(May the many sentient beings who are sick, quickly be freed from sickness.
And may all the sicknesses of beings never arise again)
(Yakushi Naori, the Medicine Buddha)
You can also use something such as these lines which are traditionally used in the practice of developing metta (loving kindness):
May I be well
May I be happy
May I be free from suffering
When I practiced mantras in a Tibetan Buddhist context they were often used with an accompanying visualisation such as the particular deity associated with the mantra (the Medicine Buddha in the case of the Medicine Buddha Mantra and so forth). This I find can enhance the calming effect of a mantra. Feel free to develop your own visualisations.
In Tibetan Buddhism (also Hinduism and Catholicism) prayer beads are often used to count rounds of mantras. Not so much in Zen but I imagine this method is also used in other Japanese Buddhist traditions that include mantra recitation as a traditional part of their practice such as Shingon and Pure Land schools. I must admit that I like prayer beads (malas) as they add something to the practice, a tactile stimuli and additional focus for the mind. As the internet saying goes, your mileage may vary, but don’t dismiss it out of hand as something esoteric.
So, this was intended to be my personal take on the use of mantras in spiritual practice and difficult times but in no way accurate about how different spiritual traditions themselves see mantras which are generally much more esoteric that my pragmatic stance. There is much material out there about which is available to anyone wanting it.
The best way to investigate mantras, as ever, is to practice yourself and find where it leads you. You may find that mantras are not for you, or else that mantra practice becomes a fruitful part of your spiritual life. Many have and still do. I count myself among them.