As someone who is recently and still kinda struggling at coming back to osu!mania after high school pressures (my exams literally start in 2 days wish me luck), I can confidently say nobody is going to be as good as where they left off, even between days.
It's like interest building from a loan, but the loan is how long you spend off the game, the interest is the rust/coldness building, and only after paying off the rust with playtime can you go back to normal and improve from there. Paying a day's worth off the game with 15-20 minutes or so of playtime is a steal. Paying a week's worth is challenging, probably will take a day or two. Paying 3 weeks or a month's worth... requires many days of the week, if not more than a week, from personal experience.
There's no issue in backtracking to improve upon what you already know, and everyone who rusts will need to start easier or else the same thing happens: frustration and whatever you call the "all for nothing" mentality. In my instance, I was able to play pretty fast jumpstream and handstream patterns, but now need to relearn how to do splittrills that appear during them. I just simply can't play what I was able to before, and that's fine.
It tends to be fun going back and seeing a map and being like "oh I remember this one! I want to play it". That's the best way for someone to get out of the block since it basically is the most fun way of telling yourself "play more", by telling it to yourself because you want to and know it will be enjoyable and fun.
Also gave me a chance to practice what I regret not practicing before, as I'm doing a bit more LN and accuracy practice than usual right now. I'm practicing to get back to something reminiscent of my previous state at the same time, though I personally find it never is the exact same.
Idk if this is like a new experience or not for you, but get comfortable with it, especially if you're going to struggle to get on osu! or any rhythm game often.