Thank you for sharing. You are not alone. I suffer the same difficulty every day. You know, people often imagine that professional writers, especially those considered "successful", just get up in the morning, fix a coffee, roll up their sleeves and start bashing out perfect sentences without flinching. But it's not true!
Every word, even from the most famous and prolific writers, is hard won. I suffer from terrible writing anxiety. But with time and persistence I've learned to write anyway - despite the anxiety, the doubt, and the fear. If you're like that, too, then this might help:
How to Write Despite Crippling Anxiety
Three steps to overcome the fear and start writing
And if you struggle with procrastination, even if you’re not especially anxious, this is how I learned the hard way to overcome procrastination as a writer. You may find it helpful:
How to Make the Journey from Procrastinator to Writer
Learn in five minutes what it took me 25 years to figure out
Anyway, I hope that helps.
One word at a time. That’s all you need to do. :)