Bhagwad Gita

This material world is full of stress and misery. The reason is people get attached to the results or fruits of their action. If we do our actions in the name of the Lord, without caring for the results, then our lives will be peaceful. This is well described in the following sloka,

"Karmany evadhikaraste,
Ma phaleshu kadacana,
Ma karma phala hetur bhur,
Ma te sango stv akarmani. "


Which means,
'You have a right to perform your duty but you are not entitled to the fruits of action. Do not consider yourself the cause of the results of your actions. Do not be attached to not doing your duty. '