Just a few short years into my career I was project lead for a client engagement building some software and managing a small team. The company had been struggling to deliver successfully and on budget, especially with this client, but my team was crushing it (in part because I managed the client tightly).
A couple months before we were scheduled to wrap up I was asked if I could free up one of my developers to jump over to another project that was struggling. I said I was supposed to get him for two more months, but that because we were doing so well I thought I could free him up and still deliver successfully.
So I let him know he would be moving to another project, he agreed, and he helped get his tasks transitioned. The next morning I came to the office and he wasn’t there - he had been let go.
I went to the lead project manager who had asked me to free him up, ready to let loose on him when he said “Dude, I didn’t know either.”