This phrase is a call to action for young people to embrace life with courage and enthusiasm. It encourages us to take risks, try new things, and to not be afraid of failure. It's a reminder to stay young at heart and to live life to the fullest.
From Wikipedia
18×2 Beyond Youthful Days is a 2024 romance film directed by Michihito Fujii and produced by Chang Chen. Starring Greg Hsu and Kaya Kiyohara, alongside an ensemble cast including Joseph Chang, Shunsuke Michieda, Haru Kuroki, Hitomi Kuroki, and Yutaka Matsushige, the film follows a recently fired Taiwanese video game developer (Hsu) on a solo trip to Japan, reminiscing about a past romantic entanglement with a Japanese backpacker (Kiyohara) that never blossomed into a relationship.