Over the years I wound up with a collection of the pencil gauges. I think in response to a thread here a few years ago about the accuracy of these things (gee, is anything new under the sun?) I went and checked all of them. I had a car tire that was inflated to like 30psi that I figured would maintain the same pressure no matter how many of these things I checked. I might not find an absolute measurement but I could gauge them against each other (no pun intended).
Found they were all over the place. I threw out all but the ones closest to each other.
Recently I picked up a Makita tire inflator which has a digital readout. Then I threw out all my other pressure gauges and now have just this one gauge. Now that I am down to but one gauge, I know precisely what my tire pressure is--and I refuse to check it against anything else. Therefore it is correct.
No Xanax needed.