Most Helpful Guy
I think you should do it whenever you want to. If it looks bad, but you are fine with that, then go without. If you are a runner and it hurts to go without a sports bra, but yo want to go without, then do it.
Most Helpful Girl
For me personally I'd never do it at school or at work, but otherwise I don't really care at all, I'll just do it if I feel like it.