One of the things I forget in training is to vary the circumstances. We train at home, in the park, at at training venues. But usually the circumstances are very similar.
Suzanne Clothier has an amusing reminder of the importance of varying the conditions:
I do not always heed commands
My dear but often silly man.
I might not sit if near a goat.
How could I lay down on a boat?
Perhaps I'd lay down in the house,
But not if I have seen a mouse.
Don't tell me "heel" when I've smelled fox
Or found the biscuits in the box.
I'd find it odd to hear words said
If you were standing on your head,
And wonder if "stay" means "do come here"
If you said it to me from a chair.
I cannot always just obey
Whatever silly words you say.
'Cause if I'm staring at the cat
I will not hear you - that is that!
We tend to see the verbal cue and/or hand signals as the cue for a behaviour, but our dogs may recognise other cues as being the important ones - body language, subtle movements, familiar settings ...