Re: New instructor on the block
IMO, the time to praise most and celebrate is when someone accomplishes something that was difficult for them or that they were previously incapable of. It's that continuous overcoming of obstacles that will drive a student forward (in any subject) and lead to improvement. If it came very easily or effortlessly, certainly they should know it was right so they can try to repeat it the same way next time, but for that particular person, IMO that particular thing wasn't enough of an obstacle to be worthy of all that much celebration yet.
That's part of why for me, someone rolling easily on their first day merits perhaps a passing comment but not really much more, e.g., Great, you're picking that up really quickly, it's good that you're remembering to (relax, keep your arm extended, keep your hips in this position, etc, whatever it is that people often do wrong that this student is doing right). Here's what I'd like you to try next.