How to achieve true lasting quietness ?

The quiet mind one gets through meditation is indeed of short duration, for as soon as you come out from meditation you come out at the same time from the quietness of mind. The true lasting quietness in the vital and the physical as well as in the mind comes from a complete consecration to the Divine; for when you can no more call anything, not even yourself, yours, when everything, including your body, sensations, feelings and thoughts, belongs to the Divine, the Divine takes the entire responsibility of all and you have nothing more to worry about.

Ref : Words of The Mother Vol. II