Day 15 → Something or someone you couldn’t live without, because you’ve tried living without it.
I'm going to avoid (doing the smartass thing and stating) the obvious: air, water, food. But, still, my answer totally relates to my post about The Can'ts. There was a long time that I thought no way could I live without X, Y or Z. You know what? I totally can. I don't need so many of the things that I have felt like I needed. And it is so very freeing to realize and understand that.
As for people... There is nobody I couldn't live without. However, doing so might surely break my heart.