By now we all should know the dangers of driving too fast, although many people still think they are safe flying round a corner because 'the car can handle that speed' That isn't the problem tho - if you cannot see round the corner then you don't know if there is an obstruction on the road ahead
So you are not just thinking about if the car can go at that speed but also adjusting your speed to how far ahead you can see.
An often overlooked danger is also driving to slow.
Some people think they are being safer by driving very slowly but this isn't the case - you become an unexpected hazard to other drivers. On single carriageways traffic can build up behind you are people get frustrated and take risks to try and overtake you - on motorways people may misjudge how slowly you are going and zoom up behind you too quickly having to break sharply or swerve into other lanes
Where a road is clear with good visibility and it is safe for you to do the speed limit you should be driving at or close to the speed limit