assume you are invisible.
The assumption of invisibility has to be understood in context - in particular, it must never prompt trying to "hide".
It's unfortunately necessary when riding on many roads that don't have a generous shoulder, to take a position far enough into the traffic lane that you have to rely on drivers seeing you, and passing you carefully. Otherwise, if you try to hide at the edge, many will be tempted to try to squeeze past you without allowing enough space, even when they do see you.
Where "invisibility" actually applies is largely with turning and crossing traffic - a bike is nowhere near as obvious as a car approaching. And drivers always underestimate or overestimate the speed of a cyclist, they
never get it right. So you'll have all of people who cut in front of you without seeing you, people who thought they had time to when they didn't, and even people who had ample time to safely do something in front of you who end up waiting an absurd amount of time, on occasion prompting those behind them to behave more rashly. And pedestrians wanting to do something like force a crossing against a light are just as bad about seeing cyclists as drivers are.
Finally there are situations where the unaware cyclist can put themselves in an invisible situations - for example, be extremely wary of passing slowing or stopped vehicles on their right (or whatever the non-traffic side is); if you have to do it, do it very slowly watching for sudden developments like turns, opening doors, or people approaching from the roadside. Unfortunately this includes situations where badly designed cycling routes put through cyclists on the wrong side of turning drivers, and doubly so where even more stupidly designed routes have cyclists going the direction opposite that of the road traffic that everyone (drivers, pedestrians, and other cyclists) are looking for.