Take a break after a meeting to recover a bit. Don't feel obliged to stay as productive as on the days that don't have meetings. If you are demanded to be as productive on the days with meetings, then you can just explain that your attentional resources are limited and the demand is excessive.
After all, you are paid for the time spent on meetings, so it's not you, but the business is the entity which should bother about productiveness of your time.
