(NewsNation) — John Ramsey, who lost his daughter 26 years ago this week, told NewsNation’s Ashleigh Banfield on Wednesday that his family couldn’t celebrate Christmas for several years after losing JonBenét.

Ramsey said he never healed completely, but he urged the University of Idaho families grieving the loss of their loved ones to stay strong.

Ramsey believes local police made mistakes investigating his daughter’s death, but tells “Banfield” it’s a good sign that Moscow police have accepted help from other law enforcement, since departments can sometimes get territorial about their cases.

“It’s time to put egos and arrogance aside and say, ‘Look, we got to figure this out. Let’s cooperate 100%’ … That wasn’t done in our case, and that was a huge mistake” Ramsey said on “Banfield.”