How do I get over my fear of highway driving?

Okay, maybe fear isn't the right word because I am not necessarily afraid of driving on the highways but more afraid that I will make a mistake on them. I got my license last year and I got my first car shortly after. I drove on the highways fine in that car. Unfortunately, I was t-boned in an intersection which totaled that car. I don't have my own car anymore but instead practice in my mom's car. Her car is a lot different to drive and not as comfortable. It's not horrible but not as comfortable as my totaled car was. We are going out this week and I am gonna be going on the interstate with her in the car with me. I am afraid that I will cause a mistake that will hurt my mom and her car. We do have collision coverage on the car but still, I don't wanna get into a bad accident again. I think my accident took away some of my confidence as well. So how do I start feeling better again? I keep trying to think of the times I was so comfortable and confident but my stupid anxieties kick in and override those positive thoughts. Any suggestions on how I can help myself improve? Thanks!