I feel you. No matter how good you think you are or how hard you are hustling, there is always someone better. That's just how the world is.
Media and the Internet has to do a lot with this - a cesspool of success porn.
One thing I like to do is look back and see how much progress I have made or all the achievements I have made so far.
We tend to forget how much we have achieved and only when we look back do we realize.
As to making a difference, you are making a difference. As honest writers we all are. The desire to make a difference makes all the difference to be honest.
This was a brave and honest post. Thanks for this!