Yesterday I was reading Leo Babauta's blog "ZenHabits" when I fell in love with the extension "Minimalist Gmail" that was developed by Matt Constantine to help Gmail + Firefox users declutter their work space.

What does it do?
Basically keeping Gmail simple and clean.
    * Choose what you want, get rid of the rest.
    * Simplify Rows takes the heart of the clutter, hiding unnecessary icons while keeping all the functionality.
    * Remove chat, but still respond to incoming requests.
    * Remove ads, if you must.
    * Hide the header, but get it back in a jiffy. We add an itty-bitty toggle arrow for quick access to the search and settings.

Of course, if you install it and you realize that you don't like it, there is an arrow just at the left top corner where you can click at  it any time you want to change your mind. You can also uninstall it from your firefox addons list.