First thing I'd recommend is to wear padded shorts, helmet, wristgaurds if you can(and are not already). Falling sucks so try and reduce the penalty in doing so. As you say, taking a bad fall can give you a mental block that will take a while to train yourself out of. The good news is you will eventually fall way way less and even then they don't tend to be the painful type.
I agree that taking another lesson would be a good idea - even if you understand the theory they will be able to see what you're doing right and wrong much better than you can and be able to give you feedback accordingly.
The things you should focus on are, awareness of you body position. Keep balanced and shoulders inline with the board at all times and a quiet upper body. You can (and people do) get away with all of these things but it will make everything more difficult. If you are properly balanced at all points during the turn, it makes it much easier to stay in control and stay upright. Instructor feedback will definitely help here.
The second is edge awareness. The more you get a feel for the edges, the more you will relax and allow the board to do it's thing and the more comfortable you'll feel keeping you body balanced. It takes a bit of practice, especially to feel really comfortable turning through the fall line but it will come. Knowing that you have good edge awareness will provide a good platform and help you control speed to a degree.
What you should be aiming for is to be able to allow the board to turn into the fall line in a smooth manner (quiet upper body), to let the board flow smoothly through the fall line with your body fighting the urge to lean back (away from 'danger') then let the board come around to the new edge as one smooth motion. If your body has kept balanced throughout, you'll start to notice that the edge change can happen fairly quickly without the need to rush it. The more you bend your legs when on an edge generally the more you will control speed. The more you control speed, the less rushed you'll feel in general and the easier the whole process gets. If you feel the board pick up too much speed as you turn (runaway train feeling) the chances are you're leaning back (in fear of the slope). That makes it take a lot longer/more effort to engage to new edge and you'll pick up speed. Try to notice the opposite - if you keep some pressure forward, you really feel the change happen positively. To use a car analogy -The difference in feeling is like going from bald front tires in the wet, to fresh tires. There wont be several seconds zero control that you may or may not recover from when you make a turn.
It's a circular loop - the more you control your body position and speed, the less you will fall and the easier it will be to feel whats happening with the board and the easier it will be to control your body position and speed
These things quickly become second nature and will allow you to safely progress to the next level.
You've already had some achievements in your progression. These will continue and whatever they are, you'll know them and will be stoked