Is it bad to wear the same bra everyday?

It is not exactly bad for your breast health, but it could be bad for your hygiene. Whether you realize it or not, you do sweat around your breast area. Having a tight fitting article of clothing around this area underneath a regular shirt, increases the warmth there obviously too. I wouldn't recommend that you wear the same bra too many days in a row just for good hygiene. After a couple-few days, depending on your body, you should wash it to eliminate any sweat odor. In the winter-time you can get away with wearing the same bra longer than in the summer time. Health wise though, there isn't really any harm.