Here's the first major lesson: Writing is not an activity. It's not something you sit down at the keyboard, and just start doing. That's called 'typing.' Typing is an activity ... Writing is a process. And if you start thinking of it as a process, life gets so much easier.
And the reason you hate writing so much is because you start analyzing your work before you're done pouring it onto the page. Your Left-brain won't let your Right-brain do it's job ... Your Right-brain gets the words on the page. The Left-brain makes them sing.