Researchers believe that the mucus in your nasal passages acts as a defense against infection, and flushing it away disrupts your body's immune function. They recommend that neti pots be used every once in a while to relieve congestion, but should not be used daily for an extended period of time. If you have issues with constantly being stuffed up, see your doctor so they can help figure out the cause of your congestion and how to treat it.
If you've never heard of a neti pot and want to see how it's used, check out a how-to video when you read more.
Source: Flickr User Thirteen Of Clubs