I currently have two problems with this:

• While looking backwards, I do not see where I am going.
• It is difficult to maintain perfectly the same direction while turning around. Probably both problems can be fixed by training on a safe place, but is this way of looking backwards a recommended and safe technique? Maybe better to avoid this? Or the clue is to learn returning back to the forward view very quickly?

The obvious alternatives are:

• If only another another bicycle may be approaching from behind, just show the hand signal to understand which side to drive around you.
• If you make something like a left turn across a car road, stop to look around.
• Engine noise (and lights in the night) from behind can warn about the approaching car.

There are also other options now like mirrors (I tried some so far without obvious success) and Garmin radar (not cheap). Anyway this question asks is it worth learning to look backwards while riding or better to learn avoiding this habit?