Everyday
Everyday is a opportunity to do better, learn from our mistakes and failures. It's owning up to them, giving up one's ego and reflecting to make consistent and permanent changes that's important. It's taking every step to become better that matters, and making up for the mistakes you've made before you make another.
We can be our own worst enemies. Failure to acknowledge our mistakes or shortcomings can bring pain to ourselves and others. They say that the road to hell is paved with good intentions and it's true. I imagine most don't wake up and say "I am going to murder, steal or hurt someone today" but something you do could lead to those results.
I have recently also discovered it's the flaws that you can't see that are more dangerous than the ones you realize. I have been so focused on my short-comings, like spreading my self out too thin and having too many projects, to pay attention to things that I didn't realize were being overlooked.
I now realize the importance to take a step back, and to reflect on your self. People often look introspectively but how often do we truly search out the things that we ignore or don't want to acknowledge in ourselves?
Learning from our mistakes is easier said than done. Habits are hard to break. It really only comes down to a few simple steps as I see it:
Step 1) Seek out your short comings hopefully before a failure.
Step 1a) Making good on a failure if possible.
Step 2) Implement consistent and permanent changes to fix any shortcomings that may have failed you in the past.
Steps 1 and 1a are by no means easy but can require the least effort of the three. The last step, consistent and permanent change, is hard. Habits and behaviors run very deep and are very hard to change. Being a big proponent of self improvement I have picked (up from a variety of sources) a number of habits and tricks to help make changes stick. Rarely have I seen techniques for lasting change succinctly described but I have recently read a excellent book called "Willpower:Rediscovering the Greatest Human Strength" by Roy F. Baumeister and John Tierney. Read this book, it's excellent and might really help you make permanent changes if your life.
Life is not always fair and more often than not we don't get second chances. Do your self a favor, learn from your mistakes and live each day better than the last.