I think empathy is a spectrum, like many other things. I'm personally not the most empathetic person by nature, I had to learn it from others (still limited) and very rarely feel that I really know what someone else is experiencing internally, if ever... especially if I don't have quite similar spots in my own history or don't think we I share many personality traits (don't think addiction necessarily implies similar traits, or those relevant to a situation). My understanding of others' experiences and emotions is typically more based on sympathy and knowledge of psychology and other things about the human experience, and it's not effortless. I think some describe this as cognitive "empathy". But I thought to post because I've run into conflicts with people who describe themselves the way some of you guys on this thread - highly empathetic, often to their detriment, very hard to detach from others' moods and hardships around, hard not to reach out and support someone... I've mostly had colleagues like this, a very few close friends, I believe my mom was like that, and of course see plenty of people like this in recovery circles. So I thought a perspective from toward "the other end" of the spectrum might be interesting here because not being aware of differences can lead to lots of misunderstandings, miscommunication, even damaged relationships and alienation. I've been there a few times in my life and sometimes it was too late to recognize on either end.
Anyhow, the suggestion is please do not just plain assume that you know what someone else is going through, that you feel what they feel, and understand their needs without communicating directly and in detail. For example, many times I have had people reaching out to me in the way some of you suggest, both in relation to my struggles with addiction and other things, and I usually know it's driven by pure good will and intention to help. However, quite often I don't like it, especially when someone does it repeatedly, especially in private, without clear signals from me that it's welcomed and I want more... and it can lead to my isolating even more, dismissive responses that hurt the person with the good will, even abandoning relationships if it's persistent. For example the suggestion: "Hey, I've been exactly where you are and if you want a friend to speak with I am available" can have the opposite effect relative to what's intended, due to the "I've been exactly where you are" part, because unless it's clear that the other person and I have many similarities in our experiences and personal style, and really know each-other well, I would not know how that's possible and it would elicit more mistrust than openness. Don't get me wrong, this is not because the intention and wording of the person reaching out is wrong - it would be due to my own somewhat skeptical and avoidant style, even possibly finding the contact intrusive, especially if I am not doing well. I would rather receive "hey, I've been thinking of you and if you want someone to speak with I am available". Notice not claiming to know what the other is experiencing and that we are friends (unless we truly are friends and have a long, mutual history).
Again, I did not intend to criticize anyone's good intentions, these can just be nuances in communication that sometimes we take for grated because we assume similarities, but it's not always the case especially given how complex humans and human experiences can be. I'm also basing this post on the many other people quite similar to myself that I've been associated with throughout my life - the other often described similar misunderstandings, rejecting help, conflicts, even when we truly try to mature emotionally and understand these things better. So I would generally say start relatively low-key and wait for clear welcome signals from the other unless you already know each-other very well.