Probably, one of you has never tried this way. Repeating a same mantra is called chanting. But, here I want you to have some gap between chantings; I mean, chant a mantra at once, then try to feel it just by subtle intention; if thought come in between, chant the mantra. Then again, feel the mantra by subtle intention.

This might en-thrust in you the power of mantra and the calmness of mind.