There is a proper way to go about things. First off, remain calm. It can be a very disturbing experience since it can be loud, unexpected, and you may even see stuff fly all over the place.
This is all normal when a spring snaps.
Next, call a qualified garage door repair company to come out and fix the problem immediately, If they recommend that you replace both springs at once, they’re looking out for your best interest since springs tend to wear at the same rate, so if one goes, the other soon will.
And that’s it. Pretty straight forward!