Have a break when you submit your thesis. Give yourself space to rest.
Have a break now and then when you prepare for your viva. You don’t need to cram everything into one hectic period of activity.
Have a break during your viva if you need one or if you’re offered. Take your time to make sure you keep performing at your best.
No-one else is going to make sure that you look after yourself or check you’re working at your best. There’s more you can do, but at a minimum have a break!