I can't say I understand the remark. It reminds me of one I heard in the 1960's..."Wherever you go, there you are."...
I always remember my friend ( a psychologist ) said
" everything is a external event. You choose how to react"
If that's the case I can't agree with it. My sister was posthumously diagnosed with bi-polar disorder. Her choice was dependent on the particular chemical balance in her brain at the time of her suicide; something over which she had no control. All the more need for intervention by those who care for a troubled individual. In this situation it's a start, much more than lot of unfortunate individuals get." everything is a external event. You choose how to react"
this means everything happens in the world externally ( outside of you)
You choose to be happy or sad ( or how to react ) - You have a choice.