Edison’s Mistakes
Edison failed in his pursuit of a lightbulb 500 times, 1000 times or even 10,000 times depending on which (probably exaggerated!) account you read. What is certain is that he made mistakes, but he didn’t really fail because he kept pursuing. He tried things, probably believing for good reasons that he would be successful, but he was wrong a lot.
All of that wrong helped him to be ultimately right.
Now, hopefully you haven’t succeeded in spite of 10,000 mistakes during your PhD – but if you arrive at submission you must have made mistakes along the way. Things forgotten, things that didn’t work out, things you can’t explain, things that are wrong… Through all of that you’ve made it to success and submission. Mistakes are part of the PhD process, both of doing the research that becomes your thesis and of developing the skills that make you a capable researcher.
It’s fine to remember you made mistakes, but not helpful to dwell on them. Understand them, but not focus on them.
Determination is another part of the PhD process, wrapped around mistakes and setbacks and failures. Determination to see things through. If you make it through a difficult path to submission, then you’ve got the determination to prepare for and pass your viva.