During our lives, we regularly go through polarities of happiness (sukh) and sadness (dukh). Krishna explained that when senses meet sense objects, polarities of sukh-dukh are generated (2.14). Praise gives us happiness and criticism makes us sad even though it is just a phenomenon of meeting of words with the ears. Life is a continuous interaction of senses and sense objects implying that polarities of sukh and dukh are an unavoidable feature for us.

While mentioning that happiness is of three types based on gunas (18.36),  Krishna says, "That which is like poison

Krishna says, "The happiness arising from contact of senses with sense objects, which in the beginning is like nectar and in the end like poison, that is considered rajasik" (18.38). Eating tasty foods like sweets or smoking give pleasure at that moment of time but cause irreparable harm to the body.

Krishna says, "That happiness is tamasic which is delusive of atman (self) from beginning till the end and arises from sleep, indolence, and negligence" (18.39). It is the sukh arising out of ignorance like sleep or laziness.

For some of us happiness can be due to the success in our lives while for others it might be due to a monastic or missionary lifestyle. Scientifically, genetics are responsible for making us happy or sad. Whatever may be the factor, the happiness we get is of three types based on the respective gunas.