It’s an easy thing to do, particularly when you’re starting out.
You stop the music, you drop out of the rhythm, to figure out where your fingers need to go next.
It’s understandable, but this is a habit you want to get rid of ASAP. If you’re practicing strumming, learn to find your next chord while you’re still strumming. So you missed the change and are playing a wrong chord or not playing any chord — so what? If you stay in the rhythm, you’d be surprised how little the audience will notice.
I’d be a rich man if I had a nickel each time I just strummed chuga chuga over muted strings during gigs because I got lost and needed to figure out the next chord. But that habit of staying in rhythm has saved me many times.
If you don’t know what the next chord is, just mute the strings and keep the right hand strumming going. If you stay in rhythm, that sounds perfectly musical.
And incidentally, this applies to other things in life, too. Let’s say, you skipped a day of practicing/exercising. So what? Just get back to your regular routines the next day. Get back in rhythm. Falling off is not a big deal, it happens to the best of us. But what separates the best from the rest is that the best gets back in rhythm, quickly.
That’s why I count this among the most important habits. When you build a habit of getting back in rhythm as quick as possible, you don’t let mistakes and other distractions get you off course. The music, and life, keeps going, as focused as ever.