Habits
Encourage, do not blame
In one line: After a lost round, say something useful, or nothing.
Why
Blame does not change the last round and makes the next ones worse: whoever feels attacked plays worse and talks less. A calm sentence keeps the team focused on the round that matters, the next one.
How to train it
For one game, after every lost round pick one of two sentences: useful information ("they have an Operator mid") or encouragement ("next one"). Nothing else.