Well, it was more something that felt right for me to do when I would ask them to mimick me. So in order to ask them to collect or invite them to mimick my collection, I start walking/standing collected myself.
Blacky really copied that in his rear, which used to my high, fast and flung up by flinging his head back. Collecting myself really slowed him down and made his rear come from behind instead of from headbanging.
By the way, something that's really interesting, is that I was dying with muscle aches in my shins and lower legs for two weeks when I started collecting myself during training sessions!
Especially when doing the piaffe like that, whew! So collecting yourself really is something heavy physically. Good that this way I discovered that myself too.
New horse book: Mandala horses!
Never stop making mistakes! Natural Dressage