To guarantee that your information has been saved for the next time you log back in, I would finish up the current section you are working on (for example, if you are working on adding W-2 information, I would finish up that W-2) and then you can click sign out in the lower left-hand corner. 

When you log back in after you've had a break, and click Take me to my return, you can select Pick up where I left off to go right back to where you were before.