You're head's a whirl of ideas, angst and preoccupations. And it's siphoning off your attention to somewhere other than the present. Force it back to reality with a bit of negotiating. Sure, your brain loves a good bargain. So you're worried about all the stuff you've gotta do tonight. Fine. Tell your brain you'll get to it later, but for now, ask it to focus on the task at hand. If it doesn't comply, create a to-do list: it's a great way to quiet all that noise.