Panera founder says one of his biggest regrets is not firing people faster — and he's even received thank-you's afterward

• Panera founder Ron Shaich says that he regrets not firing more people faster. 
• He says that it's important to have "honest conversations" quickly and not let things fester.
• Shaich writes in his book that he's even received thank-you letters from people he's fired.

"One of my greatest regrets or failings as a leader is that I should have fired more people faster," Panera's founder Ron Shaich writes in his recent book, "Know What Matters: Lessons from a Lifetime of Transformations."