As per Hinduism teachings, the best mantra for a calm mind is not to have any expectations and happiness from an external source. The best mantra for a calm mind is ‘Om Namah Shivaya’. Chant the mantra whenever you feel disturbed.
Avoid anger and hatred. Try not to expect other people to behave in the way you want. Stay away from negativity and people who spread anger. Know your strength and weaknesses.
Never indulge in gossip and avoid giving opinions. Avoid news channels and newspapers. Concentrate on doing things and you love and enjoy most.