Begin with praise and honest appreciation.
Unjust criticism is usually disguised compliment. It often means that you have aroused jealously and envy. Remember that no one ever kicks a dead log.
People rarely succeed unless they have fun in what they are doing.
He who treads softly goes far.
Each party should gain from the negotiation.
So, to prevent fatigue and worry, the first rule is: Rest often. Rest before you get tired.