naasti buddhiryuktasya na chaayuktasya bhaavana |
na chaabhaavayataha shaantirashaantasya kutaha sukham || 66 ||

The individual whose mind and senses are not controlled cannot have a focused intellect, without a focused intellect he cannot meditate, and without meditation there is no peace. How can there be happiness without peace?

na : not
asti : happen
buddhih : focused intellect
ayuktasya : one whose mind and senses are not controlled
na : not
cha : and
ayuktasya : that individual
bhaavana : meditation
na : not
cha : and
abhaavayataha : without meditation
shaantih : peace
ashaantasya : individual without peace
kutaha : where
sukham : happy

Shri Krishna so far extolled the virtues of controlling the senses and the mind. In this shloka, he echoes the same point, but uses negative inference to drive it home.

Here, he says that if the mind and senses constantly wander, our psyche is agitated. An agitated psyche will never allow an intellect to focus. And we have already seen in earlier shlokas the disadvantages of not having focused intellect or “vyavasaayaatmika buddhi”.  One cannot hold on to a single thought, in other words – meditate, if the mind is turbulent.

We may feel that there is some repetition here – why is he asking us to control the mind and senses over and over again? But consider this: reading about it and putting it into practice are two different things. If we check the daily list of thoughts that we maintain in our diary, we realize that even if we read the Gita backwards and forwards, it takes lot of time and effort to change the quality and quantity of our thoughts. This message needs to be seared into our brain for us to take it seriously, hence the refrain of this point.

Very simply put: there is no happiness without control of mind and senses.