I hope I'm wearing a sports bra.
I imagine there will be a lot of running and dodging fireballs and other aerobic activities. And when doing physical stuff like that, it's best to have some support.
But how do you plan for the end of the world? You can't always wear practical shoes and carry a windbreaker. Sometimes, while waiting for the apocalypse, the husband wants to take you out to dinner and that involves putting on heels.
There's really no practical way to plan for Armageddon. But, when it does happen, I hope I at least have a change of underwear.