It's good that you are recognizing this challenge. Write down all these critical thoughts you experience. Work on figuring out where they come from as often these thoughts evolve from the things others say to us, yet, these things are really about the failures of others and "not" ourselves.

Here is an example of how we imprint things "unknowingly" from an early age.

I taught very young children how to ride. I had ponies that I trained to be really good with very young children. One of the students I had presented me with a challenge I had not had before. This student would request that we stop so she could "rest". She did this a lot with me. I had to work at helping her prolong her ability to stay engaged.
Her mother told me that she tended to be lazy and not very athletic. Yet, she actually "was" athletic until she had to stop and "rest" in this strange ritual she had. Come to find out that when she was very little her mother was fighting breast cancer and it was her mother who would engage with her and need to "stop" and rest. Her mother must have constantly said to her, "Not now, mommy needs to rest a bit" and also looked tired and sigh which is another thing this little girl did. What this little girl did not know, what even her own mother did not realize is that this little girl "imprinted" this behavior pattern.

I had a therapist that struggled with depression and he insisted this was hereditary because his mother also struggled with it. As time went by I began to notice that any time my conversation was about my mother or me mothering, he would literally transform in front of my eyes to where his eyes would literally change into droopy sleepy eyes. My therapist had no idea he was doing this either.

We, as human beings begin learning things at very young ages before we have any sense of anything around us. This predisposes us to forming an inner critic that can affect us in ways we honestly do not know.

So, writing down these things you hear in your mind is a good place to start so you can trace them and begin to work on dismissing them as "spam in your mind" that you were somehow encouraged to think unknowingly. Often how we "treat" and "feel about ourselves" is something we were taught to do "unknowingly".