It's no good having a fragile ego if you're a writer.  It isn't like being a mathematician or a scientist, there are no absolute right or wrong answers or ways to do things.  All the rules can be broken as long as you know that you're breaking them and have a reason for doing it.  The problem is that writing is subjective.
Some readers will happily ignore the occasional grammatical error or typo if there's a cracking plot, or will forgive a slow pace or digression if the language is beautiful.  Ask two people what they think about your work and it isn't unusual to get two completely different opinions, so even joining writers groups or forums won't give you incontrovertible answers as to how good your work might be.
The only way really to be sure that your work is of publishable quality is if someone agrees to publish it.  A rejection will usually tell you nothing except that a particular work isn't what that particular editor wants at that moment.  But an acceptance proves that someone else likes your work and believes that their readers will like it too.  Without the reassurance of Discord's Child having been accepted by Drollerie Press, I probably wouldn't have had the confidence to publish it on Kindle after Drollerie closed.  The biggest ego booster of all, however, has to be when someone else asks to use your work unprompted by you. 
I can now say that with authority, as community radio station Beam Me Up, has asked to broadcast 'Salvage', which is online in Daily Science Fiction.  I'm flattered and excited.  I'll try to restrict myself to letting readers know when it will be featured, and not bore everyone to death telling them about it, but be warned!