Not a word that many of us are comfortable with or like to think about. But, frankly, you can either embrace it and learn from it or just give it up! I've been experiencing a bit of self-inflicted failure recently, and I figured I should let you all in on it since it's just not realistic to paint a rosy picture of things all the time. I have over-scheduled, over-promised and over-whelmed myself recently and, as a result, I feel like I've let some people down. I hate that feeling, especially since of course that was not my intention at all!
So, I'm in the process of trying to figure out how to fix it (if possible). I think there are a couple of steps that I can take to mitigate:
1) Apologize. Not the "we regret this inconvenience" or "I'm sorry you're upset" kind of apology, but a sincere, heartfelt one in which you take responsibility for your (in)actions and express regret. "I'm sorry I did not have your pillow done by the deadline date."
2) What are you going to do now. Let the person know what they can expect from you now. And be realistic about it, rather than getting yourself deeper into the hole with another promise you can't keep. "I hope to have it finished in two weeks, but I don't want to overpromise again so I will keep you updated."
3) Express appreciation through more words and actions. Throw in an unexpected treat along with the promised item. "I appreciate your patience with me, and I hope you will accept this free pattern and tote bag as my token of gratitude to you for your business."
I expect that this won't always work -- people are going to legitimately get and stay pissed off at you if you don't meet their expectations, but a sincere apology and course of mitigating action hopefully will bring some people back around to you.