Peace is what God wants us to have. Those who do not obey God do not have internal peace and as a result cause the world to lose its external peace. Those who obey the Lord have internal peace despite the lack of external peace around them. Internal peace is to be protected and cherished.
Here are some tips on keeping internal peace. Avoid participating in any sinful activities or indulging in sinful pleasures. There will be a big price to pay later for a few moments of such enjoyment ~ it's just not worth it! In fact, detach from all things of the world even if they're not harmful, for all things pass. Aim for eternity. Basically, if your thoughts are peaceful, you will have peace. So it all goes back to loving and living in the Lord. If God truly dwells in you, then you'll have peace.