in terms of keeping a consistant position of yourself, your chair, your keyboard and tablet, look out for visual cues.
For example, my mousepad is aligned to the edge of my desk, my chair will be placed so the middle of my screen does align to between my legs (stop laughing) and for the distance between desk and chair, I take a Pie thumb.
The tablet is also Pie thumb away from the edge of my desk but my arm will be parallel to the armrest of the chair.
This way I am always pretty much in the same position each time just by using visual cues.
However, consider that the reason for your loss of skill can be a worse state of your body and mind (bad and short sleep, depression, bad food etc.) or you simply programed your mind (subconscious mind) in a bad way.
If you tell yourself all the time that you gonna fail, that you will miss circles all the time etc., you'll gonna plant a seed each time you do into your subconscious mind and it will grow until your brain will really let you fail and miss the cirlces leading to bad performance.
This is an actual advanced topic in terms of performance coaching for entrepreneurs and top athletes, since it affects anything and everything you do, so it does affect your skill playing Osu!.
If you do the affirmation "I do improve in Osu! day by day and my performance points keep rising and rising" for 5 minutes each time before you start your Osu! seassion, I promise, you'll gonna notice massive change in like 2 weeks.
So there is just another way how to improve faster and better than everyone else, ignoring that "play more"-hype (srsly who did invent "play more"? The illuminati?)