That's UFC star Walt Harris telling TMZ Sports how he'll honor his stepdaughter, Aniah Blanchard, Saturday when he returns the Octagon ... and it's definitely going to be emotional.

"There will probably be some tears shed, I’ll go ahead and let ya’ll know right now," Harris says.

As we previously reported, Walt's 19-year-old stepdaughter went missing back in October -- and after a high-profile search, her remains were found weeks later.

A suspect was arrested and he is now facing murder charges.

Walt -- the #9 ranked heavyweight -- is now set to fight Alistair Overeem on Saturday night ... and tells us getting back work is part of the grieving process.

"It's proof that you can go through the worst thing you can possibly think of in your life, and bounce back," Harris said.

"I’m so grateful to the UFC, and to the fans, and everybody who’s supported me through all of this. And, that’s kinda been my motivation, that's why I want to go in there and put a show on for them Saturday night and say thank you."

Harris said Aniah was his biggest fan who loved to watch him fight -- and he knows she'll be there in spirit on Saturday.