This sentence is a metaphor, which means that youth is short and difficult to grasp. "Strive to Seize the Tail of Youth" expresses people's nostalgia and cherish for youth, hoping to seize the last moment of youth. "It's a pity that youth is a gecko" vividly depicts the short and fleeting youth, just like a gecko, it will slip away from your fingertips if you are not careful.

This sentence implies that people should cherish youth, seize the opportunity and work hard, because youth is only once, and once it is lost, there is no turning back. At the same time, it also reminds people not to be too attached to youth, to learn to adapt to growth and change, and to bravely face future challenges.