Print competition and sharing images is a valuable step in your learning process.
Entering print competition is a learning experience. It teaches you discipline and helps you refine your operational skill set in the same way a commercial client would have you shooting a job on "spec". You have to follow the rules. Examining the work you enter and deciding on composition, cropping, manipulation and even the name of the print come into play. Is it good enough to demonstrate your very best work?
The same thing applies to images you post in the various forums. I'll be the first to admit I'd have a hard time staying calm over the rudeness some people display when they comment. They hide behind the anonymity of their computer screens, but that doesn't change the potential validity of some of their comments.
But a group of judges who didn't find your submissions as wonderful as you did means nothing about you as a person or even as a photographer. The same applies to people who critique your images online. Take their comments as solid suggestions. Implement them when you agree and ignore them if you honestly don't, but don't let them crush your ego or your dreams.
The bottom line to how good an image is, still goes back to my favorite timeless one-liner from my old buddy Dean Collins over 20 years ago:
"Beauty is in the eyes of the checkbook holder!"