When you practice, even something new and overwhelming, pick an element of technique to focus on while you learn. May sound elementary, but I find a lot of people get note obsession, a condition where one will do nearly anything (including some bockety technique, which then gets learned) to hit the note. Also, I find that we do best when the largest percent of our CPU is occupied. If you’re just freaking out on the notes, there’s still room for the ping-pong brain, with all of its distraction and self-doubt. Ping pong brain is highly destructive: you only touch base with yourself to be a critic or a worrier, then it’s back to thinking of the things you wish you could be doing at the same time as cello practice. Bah! Not good! So give yourself more to chew on. Not only are you going to battle through this difficult passage, but you’re going to…
keep your left thumb neutral
put your fingers down gently, but confidently
make sure your right thumb is a fulcrum, not a hook of death (technical term, there)
better yet, go through your notes from your teacher and find the “greatest hits”; a.k.a the one or two things that have needed work and comments since the beginning. For me, it was to stop pronating my left hand and play with a metronome. I still work those things!
So learn a new passage or continue excavating one in progress with some serious technique in mind. It will require so much more focus that you might very well do it right TWO ways: you’ll hit the note, and with sustainable technique.