get better at cello

I’ve been playing for 6 years but I’m still not very good. I had private lessons for about a year. I told myself I’d practice every day this summer to get better, but I just don’t have the drive. I’m so lazy.
Anyways, I’m freaking out now because my new high school orchestra will only have 2 people playing the cello, and one is me. We play at all sorts of festivals and I can’t let the group down. But I just can’t seem to make myself WANT to practice. I don’t really know what to do.