I don't know why this works or if it will work for you, but it works for me like 95% of the time when I have a mild cold or something. Breathe through your nose as slow as you possibly can. That's it. Obviously don't pass out so if you feel you have to, then take a few normal breaths. It helps if you're calm and your heart rate slows down.

I used to get addicted to nasal sprays all the time and haven't used one since I found this method.