Positive Parenting Language Paradigm and It's Ok to Say No

Today I’d like to speak to the language challenge inherent to parenting; negative vs positive word choices and there impact on your child and then explore the ability of parents of disabled kids to say “no,”  not only to their children but to demands or asks that overextend and tax them in life in and apart from their family.  Can a parent be comfortable saying no when their gut tells them it is the right, preferred or healthier choice?