...but you do need to keep striving to improve. As the saying goes, perfect is the enemy of good.
When I was in music school full-time, I remember being terrified to bring something into a lesson that wasn't performance-ready. I thought my teacher would get angry at me for not being able to play my music perfectly. This was more a reflection of the music school environment than of my teacher's actual stance; I remember him telling us repeatedly to bring in works in progress, not just finished products, but I never really believed him. I let my fear of not being perfect impede my ability to get feedback that would have made my playing better.
It's true that you should practice diligently and creatively throughout the week and do your best to make strides in your playing. Private lessons are useless if you don't do the work in between them.
However, I now find myself spending a lot of time encouraging my own students to take a chance and play something in their lesson that they're still working on, just like my teacher told me back in college. Assuming you did the work, your teacher is going to want to hear the progress you're making on the tough parts of your music. They aren't just there to hear the end result. They want to help you get there.