Disregard the son, let it go.
Once mine, is now lost.
I want it back, all of it.
Alright, I did like that it was raw, but now that you're trying to elaborate on it (or maybe its just my mood), I feel the need to point out some technical issues.
The first line lacks a subject first of all. I would prefer it be there, the lack of actual English here does bother me (though it doesn't always). So I'll provide the assumed "I" in my suggestion for change. We'll start with this:
"I disregard the son, let it go." Then comes the next issue, what is "it". The only available noun for this to serve as the antecedent to is "the son", which doesn't make any sense. Now, I know i'm being more picky than is necessary for lyrics, but just consider that. Ok, now, I can guess "let it go" is just referring to a general emotion of letting "it" all (though you refrain from saying 'all' in the lyrics, so I guess it is valid for me to wonder what particular thing is being let go. perhaps the needle?) go.
Then we have "Once mine, is now lost." Once again, what was 'once mine'? Your son? I'm making an educated guess, as I assume you're not referring to the "it" which is being let go in the previous line as being lost. You seem more to mean this: "What was once mine is now lost." Which carries I assume the same meaning you wanted, but is much clearer. Or, you could be more specific, and perhaps be even more raw by being very blunt about it, "My son is now lost." To me, that strikes a lot more emotionally than "Once mine, is now lost."
"I want it back, all of it." Once again... with the 'it's. I need not myself on that front. Instead, I want to bring up another point, regarding tense. Here we have a potential revision of the first 2 lines plus this one (having not changed the tense of any of them):
"I disregard the son, let it all go.
He was once mine, now once lost.
I want it back, all of it."
In the first line the father/the narrator is disregarding the son, and 'letting it go'. Then in the second line we move to the past... "Once mine", "now lost." But is this "now" period the same that the son is being disregarded during?
-- I'm now realizing that the way it was previously does work if I were to not assume you made a mistake (I have a bad habit of doing this sometimes when I get on a roll.) "Disregard the son, let it go" could be seen as a use of the imperative tense (command form.) Though, addressing oneself with the imperative can be a bit of a confusing way to start a poem, i suppose, so I can't leave myself entirely to blame. Perhaps the father has now already lost his son... and wants to let it go... as he reflects on what was his now being lost. However, this still poses a problem in the third line (i think...). "I want it back, all of it." Hmmm... Though, again, I suppose I could see this as the continuance of an inner-monologue, as the narrator struggles between regret and mindlessly moving on. (though i must say it wasn't the easiest for me to pick up.)
(note: basically what i was going to say before i interrupted myself was regarding how "disregarding the son" (like, not paying attention to the son while he was still around, which was my original interpretation, i suppose rooting from my own personal bias and experiences) and "wanting it all back" did not fit in the same tense like that. hopefully that rant i want on did offer some other helpful suggestions along the way, though, so I'll keep it there.)
I guess I have just one more thing to say on a specific line (staying away from judging it as a whole any further), this one: "I have passion for the addiction." I don't feel it fits well right after "I want it all back." The train of thought does not progress or flow like this. Perhaps you could say "
But I have passion for the addiction." Then it transitions, and flows with this struggling inner-monologue that is going. Rather than before, where "I have passion for the addiction" just is thrown in, and could just as well be put anywhere in the stanza, it would now gain more of an importance for being there, and effectively juxtaposed with the previously line "I want it all back."
None.