Mistakes happen. We are less than flawless each day. You missed a deadline, and your work was not up to par. You did not take the kids for ice cream as you had promised or got home late when you said you would be early. You scraped the car on your way out. You lost your cool.
It happens. So, why not own it? Your supervisor is justified in being disappointed that you have not met the deadline or delivered as expected. The kids, too, and your spouse, and yes, it is annoying to get the car repaired.
If we own it and take responsibility for what we are answerable for, we can now move on and focus on making it suitable by doing what we should’ve done in the first place. People are more accepting and forgiving when we admit our shortcomings. Why lie, make excuses or defer accountability? You now not only did not meet your commitments, but you have also added to it by not being honest and taking any responsibility.
It would all be simpler if we do what we say we will do, meet expectations, and make it right when we fall short.