Do you struggle with anxiety in your day to day life or is this driving specific and new to you?
If it's the latter you might benefit from developing strategies for managing anxiety and rationalising the thoughts keeping your anxiety going.
E.g. You rushed a manoeuvre because you were worried at some future time it would become busy... but it wasn't busy in that moment. You rushed yourself based on the anxiety which then reinforced the anxiety. You need to break that cycle by changing how you react. And then repeating that. AnD repeating it.
Have you heard of exposure therapy ladders for anxiety? You break down something making you anxious into smaller, gradually more challenging steps (e.g. Driving around the block when quiet, driving around the block when busy, driving to the supermarket when quiet...) And then you focus on repeating the first step in the ladder until you feel comfortable, then the next step and repeat, until you get to the top.
There's research that shows anxiety spikes when you put yourself in a situation that frightens you but then if you stay in that situation without self-reinforcing the anxiety it reaches a peak and ebbs away. You just have to be brave enough to let yourself experience that to prove your anxiety is survivable.
Also breathing techniques help - do you know how to breathe properly when anxious? Forcing yourself to adjust your breathing can help if you start to panic (our breathing gets shallow and rapid when we panic). Slow deep breaths where you can feel your abdomen expand.
How to talk to yourself to provide reassurance (e.g. "It is not busy yet, I can take my time. If it gets busy I will deal with that then." )?
Keep a log of your successes!