How many days can you live without coffee?

I recently asked this question. It's very important for me to have a cup of coffee in the morning. My day just will not start if I do not. And it does not matter at what time I woke up.

Before, I did not notice this for myself.

And now I have a question. Is coffee a drug? Or just the vital energy become smaller and wake up without any stimulants will not work out?

What do you think?