^ this. Use a pencil to write the number of seconds. For advanced pieces you need to actually sit down and do a division and it's tricky to practice with both hands (like Fantasie Impromptu).

it's so tempting once you get the notes right to just let her rip at full speed but this was a bad habit and hard to break.

Now I try to play as slow as possible as often as possible. Only when you have it down perfect can you then start adding dynamics, expressiveness and your own take.