If you are going to fly when everyone is flying, then you’re ticket is going to cost more. Try to be flexible with your dates. If you are dead-set on visiting Paris, go to Paris in the spring or fall when fewer people visit and airfares are cheaper. But if you want to go in the middle of August? You’re out of luck. Hawaii over Christmas? Good luck!
You're not crazy for thinking that a flight price has changed after searching it a few times in your web browser. Based on the cookies in your browser, flight prices do increase when a particular route is repeatedly searched, as the site wants to scare you into booking the flight quickly before prices get even higher. Always search for flights in incognito or private browsing mode to see the lowest prices.