How do you clear the hurdle of self-doubt?
Simple, or perhaps not so simple, just keep writing. Yes, people are going to s#!t all over you, and yes, sometimes some of the things they say are valid, but the most important voice to listen to is the one that got you to write in the first place.
You may have anonymous people tell you your work is sub-par (and that’s if they are being nice). They may tell you “…you fell in love with your plot and have bad characters…” or some such tripe. The key thing is there are a lot more people out there to get input from than just that one person. Now I’m not talking about your significant other, or you mom, or your dad, I’m talking about your peers. There are a good number of websites out there where likeminded people come together. For me that place is “Write On” through Amazon. It’s a great place with a lot of different voices and great writers.
“Writers write,” it’s an old saying but it’s true. So if your hurdle is “Why am I doing this,” the answer is, “because I’m a writer.”