(I am by no means an expert so if I say something completely dumb or wrong please don't hold it against me. Also my star estimates are personal estimates from experience)
Un0fficial, the whole Beginner-Novice-Advanced-ET classification isn't 4 concrete stages, it's an entire spectrum. Beginners can play anywhere from 1 to low 3 stars, Novices can extend from 3 to high 4 or even 5 stars, Advanced is 4-6 stars and ET is anything else. I looked at your profile (sorry) and my guess is you're bridging Beginner/Novice. You're playing 1-2 star beatmaps, but highly excelling at them as far as accuracy goes.
You may feel that you're switching between them due to a bad performance, which happens to most of us. Also, keep in mind different maps can have completely different patterns, some you're well acquainted with and some you've never seen before. It's important to pracitce those you haven't seen before, it helps you become a much better player, much quicker.
If you're looking to cement your status as a Novice, begin to practice some harder maps, going from 2-2.5 stars. They'll be harder and you're likely to get B's and C's when you first play them, perhaps even fail, but continue playing them and you'll see improvement. Keep track of the star count you excell at, pass at, and fail at, as star counts are a very solid guideline to go off of.
Sorry for writing a lot, probably a bit more than you were looking for. Remember, keep a positive attitude, and PRACTICE. Good luck!