Lying to yourself is the worse kind of lying
If you lie to someone other than yourself, it is bad, but not as bad as lying to yourself.
It is very likely that the person being lied to will sooner or later figure it out.
But when you lie to yourself, the odds of catching yourself lying is very low. Over time, you will build your mental architecture on top of the lies and make it harder and harder for yourself to find and correct the lies.
I don’t know an easy way to find the lies that I have told myself over the years. Maybe becoming more and more introspective and examining all the decisions and attitudes will help. Ideally something like hypnotic regression (or other techniques with the same promise) that let you go back in time and reexamine the events in your life could be helpful to find the lies and to replace or remove them. In any case it is a costly and potentially painful process, but it must have big positive results if one can survive it.