When an instrument fails in the cockpit, it is better cover it with something, either a dollar bill or a gauge cover (if you happen to have one of those), so we won't accidentally process the information from the faulty reading. My instructor taught me to literally smash the gauge, so the status of that instrument is not in question.
This works well in cockpits with rounded gauges. Nowadays, more and more GA aircrafts are fitted with glass cockpits. Obviously I can't just smash the screen, or else everything will be gone! What are the steps that one can take to avoid reacting to the faulty reading?