The answer is whenever possible time your approaches to junctions for your benefit.
If that means slowing slightly on approach so someone in a car or van can get past before the narrowing then so be it, you still benefit.
Whenever possible straighten roundabouts out, everyone including the lorry itself and you the lorry driver benefit.
If ill timing means you have to take the junction keeping to your own lanes like good little clones then everyone loses but especially you the lorry driver.
There are some twerps out there at the wheel of lorries who try to force through on such junctions, often they will be towing an aggregate body of some sort, regularly they will be pulling a container, you have to make allowances for the type 
Last but not least, there are still some very very good drivers out there in cars and vans and on motorcycles, if you get one that allows you by their road positioning and speed adjustments and possibly a flash to straighten a junction out, please please give them a wave of thanks as they come past, they are a dying breed (having the nous to see and plan ahead, many drivers are no longer capable of this if they ever were) and being taken for granted by the ill mannered among us doesn’t help keep them onside.
So rare are they i now find myself waving an ackowledgement if someone indicates correctly on roundabouts and junctions allowing me to maintain uninterrupted progress, sadly in too many cases it’s wheel attendants in lorries who let the side down here, invariably they are sporting the stitched in place hivis whilst driving so you had a heads up they were likely to be incompetent and as usual they didn’t disappoint.