Umm, ok... I don't mean for this to be offensive, so please accept my apology in advance humbly if so...

BUT, gheez, have you checked your life stress meter lately? What you have listed are all pretty major things. I think the frustration is not from the 'whatever' spin class people are doing... it's the total package. Maybe the gym members are just the straw that broke the camel's back?

Sounds like spinning has always been a "happy constant" in your life. Sometimes when the least bit of whatever tries to mess with your "happy constant (aka spinning)" then death become them. That's pretty much how I feel about it anyway.

The odds of having every teaching day be a "ground zero" day are pretty likely in teaching. Meaning, you have a first timer. Or... people are human and they have a stupid-attack that makes them go back to ground zero. Well, if you want to look at that as "glass half full" vs "glass half empty"... it's called: instructor job security. They NEED you to keep them on track (and not at/stuck/reverted back to ground zero).

I'm with Irulan too... if you give us some specifics on what frustrates you the most, maybe we can give you some tips. Maybe you can have a little bit of your own Jonny G. meditation in class? Visualize the frustrations away.

If all else fails, see if you can take a break before you let your frustrations be a 'deal-breaker' on teaching. Btw, I love spinning too. I was a spinner first, then a roadie and mtb, and am certified through MDA. Here's happy karma coming your way.