Make a choice about your writing. When you step into the world of being an author you can hide in the closet, or shout about it. If you shout about it, you have to be prepared that things will go wrong. Plagiarism is a crime and you do not have to put up with it. You can do something about that shit. There are other things you can do nothing about. Sometimes you've just got to suck it up.
Don't get pissed off at people. It's not their fault. (Well, okay, it probably is, but why would they care?)
Keep moving forward. It's the only way to better yourself as a writer, and as a person. Work hard, try to work often. As they say: write drunk, edit sober. (or in my case not - my fingers stop working after one drink).