Why: thus, this knowledge, more secret than all secrets, has been declared to you by Krishna, reflect on it fully, then act as you wish, arriving at the single most important line in the entire text, complete freedom to actually choose, after everything explained.

In life: even after receiving the most thorough, caring guidance available, the actual decision about what to do remains genuinely yours to make, no amount of good teaching removes that final, personal responsibility to choose.

Teaching: after absorbing whatever guidance, teaching, or advice you've received on an important question in your own life, remember this exact framing, reflect fully, and then choose for yourself, the guidance was always meant to inform your decision, never to replace your own final, free responsibility to make it.