"But I tie lots of flies, I'm practising all the time!" That's not really practising.
If you really want to improve something in your tying work on that. When I started learning to tie flies and I wanted to learn a technique, say elk hair caddis wings, I would tie sets of wings down a long shank 8, cut them off and start again until I was happy they were all good enough. Then I'd tie some elk hair caddis for my box and they'd all be good enough. There are any number of videos and images around the internet for you to use as a model.Pick one you like and try to match it, look at what you've done and see what's different then try again paying attention to the bit you got wrong.
It might be a bit boring, It might not fill the fly box and it might feel like a waste of materials, but I promise it'll make you better and not just at the technique you've practised.