I was supposed to complete a task and I haven't. This is not the first time.
It is entirely my fault and I don't want to avoid responsibility by making excuses, I instead want to own up to my mistakes and improve on my performance in the future.
How can I speak to my superiors in such a way as to convey this, and then correct my actions to make sure I don't do this again in the future?
Then, in the future:
If you bring it up before a deadline, it's an issue to be addressed, after a deadline, it's an excuse.
A couple of things. First, if this isn't the first time, then it's a habit you need to break. Second, you need to get help from your direct supervisor. If you are in the habit of missing deadlines, your boss is in the habit of letting you, too, and you need to work on it together.
I suggest that you go to your boss and explain that, after missing this deadline, you realize that you have a problem that you need to fix. Point out the other deadlines that you have missed as well, and ask for help fixing it. Then listen.
Be careful not to come in with a fixed agenda, such as here's what I have done, here's how I'm going to fix it, etc. You need to have ideas about what to do, but you don't want to sound like you're doing damage control. Wait for your boss to ask you what you intend to do about it, and then explain that you don't like repeating your mistakes (as you have done), and what ideas you have to keep yourself from repeating them.
If your boss starts in with reprimands, keep in mind that you are working to solve a problem together, and once your boss is done, bring the focus back to that. It's certainly good to say that you're sorry for any problems that you have caused, too.
We all do stuff like this. I'm naturally absent-minded. (My parents were both professors, and it rubbed off on me. Not all professors are absent-minded, of course, but my parents were certainly part of the reason that they have that reputation!) I had a position in IT change management, and one of my responsibilities was to put emergency changes through by 4 pm every day. I lived in fear of forgetting this, and one day it happened. Three emergency changes got posted, and I forgot to send them through to get pushed into production.
My boss pulled me into his office and explained what happened, who I had inconvenienced, and exactly what inconvenience I had caused. I apologized, and he asked me what I was going to do about it. Well, said I, I'm going to have to make sure that this doesn't happen again. "Well, how are you going to do that?" he asked. I had to sit and think about it.
It didn't take long to realize that I was irritated at people who put through normal changes as emergency changes because they hadn't gone to the trouble of putting them in through the normal channels, and that this was my passive-aggressive way of acting out that irritation. The individual who had put the changes through never did that, so obviously my anger is misplaced. I told my boss this, and said I would have to apologize to her personally and find a better way of dealing with the problem. My boss was quite happy with that, and I started addressing the problem more directly. Interestingly, that was the last time I forgot to put emergency changes through.
Now, I'm telling you this story because you may be doing something of the same sort of thing. (You may have entirely other reasons, of course, but you do have reasons, and you don't seem to be getting at them yet.) You might do a bit of soul-searching, asking yourself why, deep down, you're missing deadlines. If you come up with some reasons (and you probably will) then share that with your boss — again, if asked. But, I've found that once I understand the underlying emotional reasons for and thoughts behind the behavior (and there always are some), it's much easier to correct. New ideas ("changing your mind," if you will) bring about new behavior.
Generally speaking it is better to explain a missed deadline before the past due date. That way you can get everyone prepared and they know why you're going to miss the deadline.
Unfortunately when you miss a deadline, the boss is going to form an opinion prior to meeting you. Opinion might be mild like, "Oh maybe Bob ran into a roadblock, I better set this right." Or it can be more severe like, "I can't wait to hear what he has to say this time!" So it's best to get to him before that opinion can form and he knows what to expect. Not only that, the stakeholders might be less forgiving and your boss/manager might be forced to take drastic measures because he can't explain something he doesn't know.
For future references, you should explain roadblocks to the boss. If you don't have any sort of regular meeting scheduled, try to get one set up to explain progress, roadblocks, what you need, etc. Don't wait for the deadline then explain things.
Just be honest. Hopefully you have a good reason for it, and not just "... I forgot".
Tell your superior exactly why that piece of work wasn't done and hope that you don't get reprimanded.
You see missing the deadline as your problem, but it's not only your problem. It's quite often your manager's problem, or a sales person's problem who has to explain this to a customer etc.
The problem that you cause by missing a deadline can usually be reduced if you give warning plenty of time ahead. Your manager for example can decide how important it is for the company not to miss the deadline. And if he doesn't want to miss it, there are actions to take - reducing the scope of the task, adding help, or in the worst case, reporting to his manager. Anyway, the damage will be much less.
So tell people early. The important thing is not that you didn't achieve what you were supposed to achieve, but the damage to the company. By telling people early, you very much reduce the damage. That's much much more important than explaining.
It happens, as long as you own the mistake to the fullest you'll be fine. Articulate carefully how the mistake occurred and what actions you are going to take in the future to prevent it from happening again. If you can sense a deadline is approaching and you are not going to make it let management know why as soon as possible so they get the heads up and can manage it appropriately.
