Morikawa won his second major in the Open last year, following his triumph at the 2020 PGA Championship with victory at Royal St George's on his tournament debut.
On Monday, he handed back the trophy ahead of Thursday's start to the 150th British Open, meaning he will now have to settle for a replica of the real thing.
"It sucked. It really did. I woke up this morning and looked at it. The replica is beautiful, but it's not the same. It really isn't. It will never be," said the 25-year-old Californian.
"But I don't want to dwell on the past. I think I've talked about that early on in my career. I always look forward to what's next. Maybe hopefully just giving it back kind of frees me up and allows me just to focus on winning this week."
Morikawa is getting his first taste of the Old Course this week and arrived in St Andrews after a disappointing showing at the Scottish Open in North Berwick, where he missed the cut.
That summed up an often underwhelming season, even if he finished fifth at the Masters in April and tied fifth at the US Open having led at halfway.
"This is a week where, look, we only get four majors a year, and we're already at number four. I don't want to look back at this year and kind of not be happy about what I did and how I prepped," he said about the prospect of defending his title.
"So I'm doing everything I can to be ready for this week, and hopefully we can put together four really good rounds."
Morikawa, who has just slipped to number eight in the world, added: "I want to give it a run. I really haven't been in contention at all this year in any tournament, and it sucks because I love being in those spots.
"I love coming down the stretch and knowing that you've got to make some great shots, make some birdies, and close it out, and I just haven't put myself in that position," he said before taking part in an event for former champions over foul holes at the Old Course on Monday.
