Addressing past failures
You get what you focus on. So one quick answer would be - DON'T!! If you spend too long addressing your past failures your brain will be focusing on picking out similar situations and might just encourage you to repeat the failure instead of learn from it.
Alternatively you can take a peek at the failure to understand why you brand it as such. Ask yourself "what have I/could I learn from this situation?"; "what opportunities have arisen as a result?"; "what change of direction did I take, and how have I benefited from this?"
Once you have brought out the learning, reframe your "failure" label and replace it with a "lesson" label.
Then decide to focus on what you can do, what successes you have had and how you would like those to be manifested in your future.
Happy reframing.