To prevent (and hopefully cure) girthiness/cinchiness, be polite as you get it tight. You may just eliminate one reason not to stand in the cross-ties!
If you’ve ever been surprised by the point of a dental instrument, you know it can take many “stab free” experiences in the dentist chair before you start to unclench your toes and relax.
Similarly, it can take months of good girthing experiences until your horse stops anticipating the “cinch crank.”