People tell stories about themselves. This is uncontroversial.
Sometimes those stories contain errors. This is uncontroversial. People sometimes deny it when they want to deny that a particular claim in a particular story is an error.
Sometimes people's stories about themselves don't match their actions. This is uncontroversial in general. People sometimes deny it when they are defending a particular story.
When people's stories and actions don't match, a common reaction is not to notice. Why is that common? That sounds weird. It's because they already fixed the story/action mismatches that they do notice. The ones they are blind to are the ones that stay. The ones they rationalize are the ones that persist over time. The things that stay wrong over time have a higher rate of dishonesty than the ones that get fixed sooner. The issues you're honest about will get fixed with a varied, unbiased distribution of speeds – you figure some out soon and some later. The ones you're dishonest about will get get fixed with a skewed distribution of speeds – you generally don't figure them out, few get fixed because you're preventing fixing them.
When a story/action mismatch is pointed out to people, a common reaction is to blame the action. They claim it's weird they did that. The action strikes them as out of character. When story and reality clash, people tend to side with story, except in certain scientific contexts where a lot of effort has been put into getting people to respect reality more.
When story and action contradict, it's more often the story that's wrong. You can't act out of character very often, or those actions would be in character (would be normal actions for you), since you do them often. Acting out of character has to be an uncommon event. But telling false stories about yourself can be common, and is.
People often naively believe that their own stories about themselves are mostly true. They sometimes extend this gullibility to the stories of many people in their social group. Sometimes they participate in creating the stories about their friends, family, coworkers, etc.
A major step towards a reality-based view of yourself is to learn what lots of the common stories other people tell are, and to recognize many of them as false, and become good at catching people's lies. Once you're good at that, then you could be suspicious of any of your own stories that, if someone else said it, you'd think it was probably false. You could investigate those stories further using the same methods by which you would question someone else.