The Greatest Block To Healing
Denial wears two faces.
One face says, "Nothing is wrong." An adulterous spouse, after being caught online sending love message to the OP (other person), claims that he/she is not doing anything wrong.
The other face says, "Something was wrong, but it won't happen again." A parent who has verbally, emotionally, and physically abused a child for years escapes responsibility over past mistakes by rationalizing that he/she is no longer doing it.
Denial is a toxic coping mechanism. It minimizes, discounts, jokes away, rationalizes, or relabels destructive behavior by hiding behind euphemisms (e.g. an adulterer is just "making friends," a toxic parent is a disciplinarian for the "good of the child").
Things start healing only when they become what they really are. That's what denial is preventing or blocking to happen.