Perhaps she means that, unlike alcohol, she has an endless capacity for this lover. However, it also carries the subtext that - like alcohol - too much of him is going to harm her. She realises this ("be prepared to bleed") but can't quite tear herself away from him. The tone is definitely ambivalent - she's seen this one from both sides too.

BTW, check out the more recent, darker-voiced, jazz-tinged way Joni sings this song now (she re-recorded it). I don't often say this, but I like both versions equally well. One is a younger woman's voice, still with things to learn; and the other has been there, done that, seen it all. And survived.

A Case Of You

- Joni Mitchell

Just before our love got lost you said,
"I am as constant as a northern star."
And I said, "Constantly in the darkness
Where's that at?
If you want me I'll be in the bar."
On the back of a cartoon coaster
In the blue TV screen light
I drew a map of Canada
Oh Canada
With your face sketched on it twice
Oh, you're in my blood like holy wine
You taste so bitter and so sweet
Oh I could drink a case of you, darling
And I would still be on my feet
Oh I would still be on my feet

Oh I am a lonely painter
I live in a box of paints
I'm frightened by the devil
And I'm drawn to those ones that ain't afraid
I remember that time you told me, you said,
"Love is touching souls"
Surely you touched mine
'Cause part of you pours out of me
In these lines from time to time
Oh, you're in my blood like holy wine
You taste so bitter and so sweet
Oh I could drink a case of you, darling
Still, I'd be on my feet
I would still be on my feet

I met a woman
She had a mouth like yours
She knew your life
She knew your devils and your deeds
And she said,
"Go to him, stay with him if you can
But be prepared to bleed"
Oh but you are in my blood
You're my holy wine
You're so bitter, bitter and so sweet
Oh, I could drink a case of you, darling
Still I'd be on my feet
I would still be on my feet