I had a wonderful demonstration today of the point that you often make about telling children what they should do rather than what they shouldn't!
I was having my eyelashes dyed and had been in a state of sensory depravation while the dye took, lying down with cotton pads over my eyes which were stinging and dry and feeling uncomfortable.
The beautician said 'avoid opening your eyes' and of course all I heard was 'open your eyes' so cue an eyeful of stinging dye!!!
If she had simply said 'keep your eyes shut' then there would have been no confusion!
So I will now try hard to say the 'dos' rather than the 'don'ts'