If you have a personal Gmail account (or several), you can sign in to multiple accounts at the same time, allowing you to switch back and forth between them with the click of a button.
To add other accounts (Multiple Sign-in), follow these steps:
Step 1. Click on your email address in the top right hand corner of your browser (it has a small downward arrow next to it). This will drop down the option to add another account. Click the Add account button.
Step 2. A new sign in page will appear. Enter your alternate Google Account credentials here (your second account, third, etc.).
This will sign you into your other Google account in a new tab (or window - depending on your browser). You can now use either account simply by switching tabs/windows.
Step 3. If you close the second tab/window, you will still be signed into both accounts (unless you specifically sign out).
To quickly switch between them, click on your email address in the top right hand corner of your browser.
You will see a listing of all Google accounts that you are signed into. The active one will be displayed at the top in white. To switch to an alternate Google account, simply click on the one you want (e.g. firstname.lastname@example.org in gray below).