My AirPlay icon disappeared on my MacBookPro...What's going on?!

I bought my MacBook Pro fall of 2012 & I just recently bought my Apple TV. I've been using them together with iTunes & AirPlay Mirroring, but today when I tried to use it, my AirPlay icon was GONE from the top of my screen. What happened to it & how can I fix it?! I spent lots of money on my Mac products & I need them to work. Please & Thank you 🙂