It means that young people are frivolous and arrogant when they look at things and deal with them. They don't think carefully, they always take it for granted and are self-righteous. This is an arty limerick written by modern people, but it is just a patchwork of ancient poems.
It means that teenagers are very frivolous, flouting rules and degenerate, which is quite different from words such as self-confidence, heroism and youthful vitality. Neutral or derogatory. Generally speaking, it is used as an exclamation point. It also means that calves are not afraid of tigers and always feel that they can support everything. I am not calm enough to do things, and I feel dispensable when I see anything.