My Poetry. WHAT AM I?

I genuinely need you to survive;
You are the thing that keeps me alive.
I swallow you faithfully each day,
And you help me in your quiet, essential way.

You are sometimes heaven-sent, it's true,
A needed aid for which there's no need to repent.
You soften the aches and the sharp pains that are real,
The daily suffering I often feel.

You stabilize the turmoil within my mind,
And for that relief, you are truly one of a kind.
I often wonder what would become of me today
If you suddenly chose to leave and not to stay.

Would I collapse into a nervous, chaotic wreck?
A struggling joke? A burden around the neck?
So for now, I must gratefully depend
On you, my vital, silent friend.

Continue to make me well in this uncertain day,
Work your steady magic in your own special way.
You are the unseen foundation, holding back the fall,
The smallest comfort that means everything of all.

 What am I ?