My words are always positive and encouraging.

That was great does almost nothing. It's kind in intent and weightless on arrival, because it could have been said without reading a word of it.

The version that lands names something: the third paragraph is where it starts working, or you handled the interruption at eleven minutes without losing the thread.

Specific praise is harder to give — it requires having actually paid attention — and it's the only kind anybody believes. Encouragement isn't the opposite of honesty. It's honesty aimed at what's working, offered by somebody who was clearly there.