who cares?

The other day I was talking with my mom about a friend of mine, whom we will refer to as Lambo. I've known Lambo for 11 years now so it's been troubling me to see him be unhappy lately. He's come out of a bad relationship and seems to be lost. He worries me. I don't think he's a danger to himself or anything but I just want him to find his happy and get back to his normal self. I have continued to worry and reach out to him and as I was telling my mom about it she stopped me and said "leave him alone". I haven't been pushy or anything but the point she is trying to make is that I can't do anything for him. He needs to figure it out for himself, even if he makes a wrong choice along the way. I found myself arguing with her immediately. It was as if she was saying "Sarah, don't care so much about Lambo or the decisions he makes". Is really that what I need to do? Stop caring so much about him? Or stop showing him that I care? I have trouble with this. I feel like part of me just wants to show him that he isn't alone, but I also hope that he already knows that.
Beyond Lambo, should this be an approach I take to my other friends too. If I worry about them, should I just start keeping it to myself? Now, none of my friends are suicidal or at serious harm; obviously if that were the case I wouldn't be discussing it here and not with them. For example, my friend Rum Runner likes to drag race and do silly dangerous things. Obviously it's nothing to lose sleep over but I still worry a little about him. At the end of the day, I don't want to be that friend that's like having a second mother around but I also don't want to be absent from a friend in need. It's a hard line to walk.
So, I guess for now I will leave Lambo be and if he needs to talk he knows how to get a hold of me. And Lambo, if you're reading this, just know that I want what's best for you and you deserve all the happiness in the world. And I adore you!