Step 1…slap yourself in the face for even letting it happen!
Step 2…if it is already dry or close to it, take a FRESH blade and 'slice' off the heavy drip best you can.
Step 3…at a 90 degree angle, 'sand it down'. If it is still wet or semi wet, do this gently!
Step 4…sand with a lower grit paper
Step 5…sand with a higher grit paper
Step 6…Hopefully your done and can continue with your life. If not, slap yourself in the face again and read below.
Sometimes you may even need to end up filling it in with filler to even it out. Because I am VERY picky and want a perfect seamless look, I end up doing this much of the time. When this happens you have just added another hour or 2 to your work because now you must wait till the filler dries, hit it with primer, let that dry, sand, THEN you can paint.
Bottom line…DON'T LET IT HAPPEN! But in the event that you think your extra awesome that day it won't happen to you, these tips will hopefully help:)