Most times the fault isn't with others, it's with ourselves. When relationships, finances, health, diet, education, etc don't seem to work out the easiest thing to do is to first make excuses. 

If we are at fault, we can look back on choices we made, and see that we contributed to our own failure. We learn from our known mistakes.  We grow and we are able to use this experience not to repeat the mistake 

When we deny our own mistakes, we learn nothing because we feel we did nothing wrong. 

Therefore we are doomed to make the same mistake over and over and over and again.