This basic email transaction is common for me recently:
Email: Hey Chris, are you interested in doing this thing? It’s a fairly major request that will take lots of your time.
Me: That thing sounds awesome, but I’m afraid I’m just too overcommitted already to add anything new.
Email: We’re very disappointed.
It was already hard for me to say no. I’m aware that’s not an awesome email to get. You were hoping for a yes, and I couldn’t come through. So now you’re going to make me feel even worse by making sure I know that you’re disappointed.
Well, sorry, backfire. Now I’m annoyed at you.