I have certain rules that are "always the rule" - good manners, respect, kindness toward animals (my son has 3 cats) but others, in areas where I know he stresses, we flex when needed. Example: I caught him clearly lying to me the other day, and lying is against the "always" rules, so there had to be punishment, but it had to be punishment that wouldn't cause further problems. I told him to sit on his bed (quiet, dimly lit room) until he was ready to tell me the truth. He missed his swimming lesson, but finally after 2 hours of time out (he's 11) he owned up to the truth, had to clean up the mess he'd made, and the crime was forgiven.

I think forgiveness, explicitly letting the child know the episode is over, is really important to SPD kids. Mine will obsess on his mistakes unless I make it clear "you did the crime, you did the time, we're done now."