Bitterness

The tea and the muffin tasted more bitter....
I would never know those two things tasted so damn bitter before.
But when I ate it.... when I drank it.... my tongue felt something.....
It sent signals to my brain, and said it was bitter.

What is bitter?

I wish I have known it before.
I used to drink tea without sugar, and never felt bitter before.
I used to eat chocolate muffins before, and never tasted bitter.

And why it tasted bitter today?
After I saw you?