Chapter 2 · The Yoga of Knowledge · Krishna said
Bhagavad Gita 2.66 — No peace, no happiness
नास्ति बुद्धिरयुक्तस्य न चायुक्तस्य भावना। न चाभावयतः शान्तिरशान्तस्य कुतः सुखम् ॥
nāsti buddhirayuktasya na cāyuktasya bhāvanā | na cābhāvayataḥ śāntiraśāntasya kutaḥ sukham ||
Meaning
One who is not disciplined has no steady wisdom and no deep devotion. Without devotion there is no peace, and without peace how can there be happiness?