If you find yourself Googling ex girlfriend quotes than you are not mentally in the right state (if you ever want her back). Posting sad quotes that are directed at your ex girlfriend puts you in a submissive state. This is not attractive and is not going to guilt her back into your arms.
Posting those ex girlfriend quotes on your Facebook, away messages, or any other social media network is going to hurt your chances of getting her back. That is an act out of desperation and shows that you truly need your ex girlfriend and are upset not being with her.
Even if you are devastated by not being with your girl, you can not let her know that because it will be used against you. Posting those quotes will indirectly push her further away and give her a sense of satisfaction and control.
When I went through my devastating breakup my ex girlfriend would put some of those quotes up and I would immediately look for retaliation quotes to top hers. Little did I know that I would have been better off writing that I was out with friends on my away messages.