When you work or learn something in a specific place, your brain may associate that location with working and focus. When you arrive at the office, your brain is prepared to start working. When you enter the bedroom, you may feel relaxed or even get drowsy.
So, if you have a big presentation coming up, for example, it can be helpful to practice in spaces similar to the one you'll present in. Sit in the seat you'll be sitting in--and walk up to the podium. You'll be amazed how those simple actions settle your system for the day you speak.
Additionally, setting up a consistent workspace that you are comfortable in will prime your brain to work every time you get there. This reduces the amount of time it takes you to get focused on the tasks at hand. And it will help you stay focused all day long.