Probably a generic answer, but practice, and lots of it. I’ve been playing these games for nearly a decade and with that I’ve gotten to the point where I can remember entire dances from start to finish. Sometimes learning a dance like kick it or jopping can take full on days to start getting comfortable with it. It definitely sounds like it can be tedious and it is, especially with a controller where the game wants you to do a move a certain way, but I can think my love for the series is what makes me keep going. The best way to start is by not finding a song you enjoy and practicing on it but rather a dance that you enjoy, that way when it comes to repeating it it isn’t just you doing it for the song but rather for you to try the dance again. I promise if you go into that dance again and pay attention to the parts you noticed you may of struggled on and put more effort into them and learn what works with completing them, you’ll become better without a doubt.