One particularly big misconception is that if the horse is seeking the release then it must be a logical conclusion that the horse wishes to avoid contact.  Nothing could be further from the truth.  A horse that understands contact is not afraid of it and doesn't suck back behind it.  Some practice is needed to ensure that the horse learns how to assemble his body in response to the contact without becoming tense.  

When to release

The release serves multiple purposes.  It says to the horse 'yes that's right' -- just as the click does.  It ensures that the horse is free to perform the requested movement.  Finally it serves as a test of the balance, since if a release results in the horse losing his balance then he wasn't confirmed in that balance.  

It would be, however, a grave mistake to withhold the release for fear that the horse will make a mistake.  The only way to know if the balance is there is to release the contact and see for yourself. 

Sometimes the horse does stiffen against the rein and this would not be the ideal time to release.  

	Asking for reinback.  The foot are moving but Tulsa but she isn't allowing the rein aids to go all the way through her body. So I will stay in the reinback until I feel her make a change in her back. Then she makes a change and ...
	... I release.  Though not to the buckle in this case.  Instead I gently reestablish the contact and carry on.  This horse still struggles with finding the point of release.  When she is clearly more comfortable with it I will add more to the equation without needing to throw the reins away. Notice the change behind the saddle.  That's the change we need to see in the reinback.
	Riding on the buckle in trot or canter is a good test of relaxation as well as a nice way to warm up.  Letting go, being willing to let go, is just as important as being able to communicate something clear through the reins.  This horse is clearly neither bothered by the contact above, nor unstable completely free.