Driving instructor here, I try and teach my pupils to always drive defensively. Always be aware or what is around you, to the side of you, and very importantly behind you because this helps you with any speed/positioning decisions. You should be safely checking your rear view mirror every 5 seconds. Always leave lots of space between you and any other cars, if someone is tailgating, make sure you extend the gap between you and the car in front.
Be looking as far ahead as possible and planning for hazards that you see long before you get to them...e.g if on dual carriageway or motorway, and see slow moving vehicle in left lane, prepare in good time to overtake by checking mirrors and maintaining your speed. If you see anything in the right lane let them pass then move over, if they are far behind in the right lane, then maintain speed and move out.
If on a road with many parked vehicles, assess passing places on either side of the road, if you're not sure and an approaching vehicle is coming, wait in a decent hold back position of at least 1 car length.
And definitely yes, prepare for any journey by looking at street view, even I do this. I occasionally use a sat nav, but always check my route on google first so I have a vague idea of the direction I'm going in. Even if I'm doing a long drive. I assess the motorways I need and have satnav for the town/city driving.
As another poster says, the signs and road markings are all there to help you progress safely so look out for them in unfamiliar places. I do think it's so important to keep trying with the busier roads, maybe familiarise yourself with them at quieter times of day/evenings.
Your instructor should have taken you on busier roads/junctions though. Round where I teach there are many extremely busy roads and junctions that my pupils work up to. I would never dream of letting a pupil go for a test if they hadn't experienced busy roads and junctions. Crazy.