I did not have the privilege of playing junior golf (didn't start til Senior year of high school), so take my advice for what it's worth.
I did play many sports from grade school on up, and I would imagine that the coach's are all looking for the same thing. They want someone that has potential for growth and a good attitude. Based on the fact that you usually shoot in the mid-40s, it sounds like the potential is there. You just need to make sure you take a good attitude with you to the course. If you hit a bad shot, just shake it off and hit your next one better.
Also, it sounds like your golf coach is confident that you have what it takes to make it, so don't make yourself sick worrying about it. Just let you natural ability take over and keep the positive attitude.