“But” splits the sentence in two. When we say “but” we negate everything before it. “I’m sorry you feel that way, but…” is an empty sentence, an attempt at reconciliation that is likely to leave the listener feeling alienated and misunderstood. “You did a great job, but…” leaves the receiver hanging on to the criticism at the end of the sentence, and might miss the compliment. “But” erases and negates, emphasizing division.
“I was once asked why I don't participate in anti-war demonstrations. I said that I will never do that, but as soon as you have a pro-peace rally, I'll be there.”
-- Mother Teresa