Try this little secret of writing 15 minutes a day. And don't worry about the mistakes. You need to just write "raw". Let it flow. To start with, be careful and watch that you don't go over your time limit very far. If you do, then later you may not want to, because of fear you will end up spending more time than you should. Well maybe, anyway! If you are okay with that, then go for it. Sometimes it is easier to set yourself small goals first. Then when you get started your inspriation flows and you will not want to stop while you are in the thick of it!
Do this for several days or weeks so you have a collection. You can do this in longhand in a spiral notebook for example, or you can sit down at the computer and type. Sometimes I find that I can keep up with my thoughts faster if I type. On the other hand, sometimes I like writing it out by hand, because it makes me stop and think. Whichever way you do it, it needs to be double spaced, so you have room for editing. Either way works.
After you have written some, then go back and reread what you have written. But do this after it has been a while since your wrote it. Once it sits and becomes 'cold' it will be easier for you to make revisions. When you write the first time, you know what you intend to say, but don't always get it on paper. When it's "cold" you'll pick up on that quicker.
If you make this a habit, say, just before going to bed each night. Then after a year or so, you will be surprised what you have recorded. And it only took you a few minutes ...at a time, to do it!
Happy Ghost Busting.