There is a difference between validating someone's grief (and there is no better validation than sharing a similar personal experience) and actually encouraging the expression of grief by framing the experience as an exceptionally bad one. The best way to deal with a negative experience is to frame is as a normal occurrence of life, and not as some extraordinary misfortune.
If you're an alcoholic at the end of your rope, you don't go to a psychologist who will tell you that he understands your pain because your life is extraordinarily bad; you'll go to the AA where you'll hang out with a lot of people for whom your experience is normal, and yet managed to leave it entirely behind. (As much as it's allowed by the dynamics of addiction, of course).
This in no way implies that the clinician has to dramatize life.
In my professional opinion, that clinician would then be negligent if they did not also (at the right time) advocate for their client to explore healthier forms of self-soothing and self-care, and to deeply and honestly reflect on how alcoholism has affected their life.
While seeing this clinician, this same client might also benefit greatly from regular attendance of a 12-step program (which, unless an explicitly closed group, are populated by people in all stages of recovery: from actively using all the way to decades of sobriety).
“That sounds really hard! I’m sorry to hear that.”
Then, just wait! don’t say anything else (yet...). Just BE with the person in however they respond. You don’t need to solve their experience by offering any of the rest — those statements can work later, and it’s important to follow the organicity of their process and not go too quickly.
When we are given space, permission, and a safe witness to our feelings, this is one way to facilitate the resolution of trauma — our bodies know how to do this, naturally.