How to turn off the ambient meter on my Honda Civic 2013?

It makes me paranoid because i'm so focused on trying to stay in the green color while driving. I heard I can turn it off but i don't know how.

Look into the Owner's manual, it's in there to show you how to turn it off. If you can't find it then take a look at the following links:
http://honda.ca/Content/honda.ca/en/2013/accord_sedan/ex_l_10164/GenericLink/TechnologyReferenceGuide_EN.pdf

Look at this forum thread:
http://www.9thgencivic.com/forum/audio-video-navigation/7518-ambient-meter-around-speedometer-stops-working.html

Or to down load the manual (FSM): You'll have to look for 2013 Civic:
http://www.filecrop.com/honda-fsm.html
http://www.manualtown.com/honda-fsm/

Hope it help. HTH

Get a hammer and give it a firm "bash". That'll turn it off for sure, forever. No more stress.