Good or Bad?

Yeah definitely brightness effects the eyes..try to reduce and use it.

I always keep the brightness to minimum, it hurts my eyes.

I think it depends on the amount of light that is present in the area where you're using your phone. If you're under the sun, you might not see the screen and a higher brightness won't hurt. If it's dark, the minimum could be too much already, but it's the lowest you can get. It can also depend on the quantity of bright colors on the screen.

I tend to get headaches if the contrast is too bright. I have to keep it at a minimum brightness.