I feel like I have a natural speed of typing where I don't have to think about what I'm typing-- it just flows.

If I slow down too much, I lose the flow and have to start thinking about exactly what letter I need to type next.

I try to slow down enough to be very accurate, but there's a limit to how much that helps me.

I have that with music, where if I slow down a piece I sometimes can't play it at all. With typing, it never gets that bad if I slow down, but it doesn't get more accurate really.

Definitely have a similar experience, feels quite discouraging in a way as your speed has slowed down but your accuracy is still the same.

I could only think a few reasons why we're making the same rate of mistakes, one is we tend to go one or two step ahead of the current word, say the word is "Stop" then the next word is "The" we tend to type the next word (The) making our mistake to be "Sthe" or could be we tend type additional letters like "ed" or "s" -- "Stops" .

Another reason for this could be the foundation of our touch typing might not be solid enough to make your fingers go to that specific key. With this issue I recommend typingtest.com for better basic lessons.

Music could be an hindrance too, when your music is kinda fast or slow, your hand movements follow that music's rhythm.

typing test is bad for you. Believe it or not, it only lowers your score. I tend to think that they are a little to harsh. It labels your score, and often makes you nervous that you are not doing your best. I know I don't do well under pressure. So try not to try timing yourself. It turns out that one after another typing test you get better. Like it like hmmm... one typing test is easier now that you tried the other. But once you go on another one, your horrible.