I have full permission to write badly. Because English is weird. Even native speakers sometimes struggle with grammar rules and spelling, so for me that English is as my second language, or maybe third, it’s completely normal. Another reason that I can relax when writing is the fact there is another stage in writing called editing. I should first put the words on paper and then I can fix it.
There is nothing to be afraid of when writing. Readers won’t see first drafts and they never know how my writing was bad at first. Just write and try to be as creative as you can. Put them on paper and you can fix them later. Writing is rewriting.