It's kind of amazing how tough we can be on ourselves. We could be in a room full of clones of Simon Cowell, Janice Dickinson, and our own mothers and still be our own harshest critics. Being frustrated with yourself whether you feel like you could have done better or you should be more focused or you should have known that, is a pretty terrible feeling that has a two-fold effect on us: We are simultaneously at fault, and our own judge–we are the victim and the offender. But honestly, getting frustrated with yourself is pretty useless. Personal frustration is the point where bodily or mental limits meet personal expectation or potential. Even when our expectations are too high, when we simply cannot meet them, we feel an immense amount of disappointment. We feel like failures, helpless failures. AND THAT IS JUST THE WORST.
So, okay. When you are feeling absolutely terrible about yourself and not meeting your own expectations, first, take a breath. Then, instead of concentrating on all the things you woulda-shoulda-coulda dones, leave your actions in the past. Like many other times in life, it's important to sort of sever that connection between your actions in the past and your emotional reaction to them. It's difficult, but in order to objectively see and really be able to learn from your own actions, you really must try to separate from the situation.
Second, um, are your expectations of yourself attainable? I don't mean that in a catty way. Sometimes we create expectations that are simply unrealistic for any number of reasons. But either way, it keeps us from actually attaining our goals. So when you're reflecting on how you totes failed yourself, ask yourself if your goal was realistic. Setting attainable goals is just as important as meeting them. If you understand how you work, you can set goals appropriately, maintaining that balance of being able to actually complete the mission, but also pushing yourself to do so.
Also, Just because you did not meet the goal does not mean you failed. You still worked your butt off and you still tried, and that deserves recognition. If you know that you did the best you could, then take a step back and make peace with yourself on that note.