Day, in his first meeting with the media since the Buckeyes' 29-23 loss on Dec. 28, joked he was now pondering the loss "every other second as opposed to every second."
"I'm just telling you it's hard to let go, and we're not going to let go," Day said. "You have to move on with your life, but at the same time we talked to the team -- we're not going to just flush this. This is going to be here for a long time. And that's the way it should be.
"We felt like we had a chance to go win the whole thing, we didn't do it, so it's going to stay fresh in our minds."
Some calls went in the Tigers' favor at critical times, and quarterback Justin Fields threw an interception in the end zone on the final drive as the Buckeyes finished the season 13-1.
The good news for Day is that Fields, a Heisman Trophy finalist, will be back for another season, along with the core of the offensive line. The bad news: Running back J.K. Dobbins moves on to the NFL along with some key receivers and defensive All-Americans Chase Young and Jeff Okudah.
Competition for the spots will begin in earnest with the start of spring practice on March 2. Fourteen incoming freshmen, including quarterbacks CJ Stroud and Jack Miller, enrolled early and will participate in spring workouts.
Freshman Master Teague III is the likely replacement for Dobbins, who rushed for 4,500 yards in three seasons. Teague ran for 759 yards in mop-up duty, but Day said he'll have to prove he can carry the load as the starter.
Day, 40, was voted Big Ten Coach of the Year in his first season after replacing Urban Meyer.
"When you go 13-1, you win your conference championship, you win the rivalry game [against Michigan], that's a hell of a season now," Day said. "I mean that doesn't matter where you are. That's a hell of a season. But we didn't reach all our goals, so that keeps us wanting more."
He said he's glad the national championship game, where LSU beat Clemson, is over.
"It was hard to watch, I'm not going to lie," Day said. "It was very difficult. I told the team and the coaches that I wanted everybody to watch that game, as hard it was going to be, from beginning to end and think about things and how badly they want to get back in that game next year, back in that situation, and what are they willing to do, and what are they willing to sacrifice to get there."