I'm wondering if we don't care about someone, we let them do what they want and we don't say anything to them about the way they live their life. But when we DO care about someone, then we should, can, and do speak into their life when we see them doing something we don't agree with or when we think they are walking off a cliff in their life.
Now, the interesting thing about this is how far we go with that "speaking into." If we care, we are to say to them, “I don't think that's right," or "right for you," or "I wouldn't do that," or "If I were you..." but then that's it - and no further. It's the difference between nagging and caring; between manipulation and concern.
So, say something, but either way, always allow the person to still do it their way - but say something, don't just let them walk off the cliff... IF you care about them... (If you don't care, then let 'em walk off the cliff - but that's not what a Christ-follower would do. Christ calls his people to be our brother's keeper.)
"Now this roof has got a few missing shingles
but at least we got ourselves a roof.
And they say that she's a fallen angel...
I wonder if she recalls when she last flew?
There's no point in pointing fingers
unless you're pointing to the truth.
And I will be my brother's keeper -
not the one who judges him.
I won't despise him for his weakness.
I won't regard him for his strength.
I won't take away his freedom.
I will help him learn to stand.
My friends ain't the way I wish they were -
they are just the way they are.
And I will, I will be my brother's keeper."
~Rich Mullins, "Brother's Keeper" (1995)
And these are some of the things a Christ-follower can (and should) say and do. Get involved a little. Speak into a life. And then honor that life more by allowing that life to be lived - their free will exercised, and their wishes chosen. Speak into people's life once and then leave them alone, to consider what you've said.