There is something about being in a class and watching a lady in her 70s do something that you can't that is pretty motivating for me.
The instructor also has to be the right fit for you for it to work. I know when we've had substitute instructors its not the same for me anyway.
I'll give one example of an exercise I could not do when I started these classes. Laying flat on my back, legs together, straight, also flat on the floor, raising myself up to a sitting position. I'd watch these older ladies do this like it was nothing and no way could I even get close.
Turns out it wasn't weak abs that were my issue, it was my hips. Instructor had me spread my legs out and try...boom, raised right up. Ever since then I've been working on building strength and flexibility in my hips and I can now perform this move fairly easily as long as it's early in my workout. As my hip flexors get tired, it gets much harder.
The instructor is also very good and pronouncing proper posture at all times and this is also an area that I was really bad at...forever. Now, whenever I catch myself slouching, no matter where I'm at, I instantly rise up, super tall and stick my chest out. Recently I drove an RV to Spokane, WA...13.5 hours one day, 9.5 hours the next. In the past this would have tore me up for days... This time I got out of the RV after the second day and went for a long walk, feeling great.
I've learned having proper form, posture and angles while working out is super important if you want to work all muscle groups evenly, properly and safely. Having an example to follow in a class that also keeps you honest is a great way to accomplish this.
Again, never EVER thought I'd be "that guy"...