How can I stop my progress but come back tomorrow where I left off

When using the TurboTax online editions, the information you enter on the tax return is saved as it is entered.  You can sign off the TurboTax online account and come back to where you left off at any time.

Click on Sign Off at the bottom left of the TurboTax online program screen.

TurboTax Online saves your work as you go, so you can exit at any time.  When you sign back in, you will be able to pick up where you left off.  

The desktop program will ask you if you want to save your work when you close the program.   You can click on File on the top menu, then click on Save, to save your work as you go.