Hi Mikhail, Just to add that I think this should read 'onto' (preposition) rather than 'on to', and although this might seem like a small point, it is a difference a dictionary will make. If you look up 'onto' you might be surprised by the different meanings of this little word. As an expression 'being onto something' implies 'significance' - to have information that will help you make an important discovery, so in the context of your quote it might mean, that once he realised/knew he wasn't a bad person (because he made mistakes) he 'discovered' he could think positively about himself and become a more accomplished/skilled person. HTH

To be "on to something" means to have some exciting ideas. Usually, the phrase refers to something like a "clue" to a mystery or an investigation. But the phrase can you used in any context. For example, if I am exploring possible careers in my future, and I think that sever specific careers look to be very exciting possibilities, I might think or say that I am "on to something". Basically, the phrase means "I have found something". .

I was on to something = I solved the problem/found a solution