الشباب شعبة من الجنون

“Youth is a branch of madness.”

This does not contradict what is reported from Sufyan Thawri (Rahmatullahi Alaihi): “O youth, perform qiyaamullail, because goodness is only in youth,” since youth is normally a time of strength and energy. This is corroborated by another hadith: “Your Lord is amazed [in a manner befitting Him] at a youth who has no youthful passion.”

Zamakhshari said, “Youth resembles a portion of madness because it overpowers the intellect and its companion is inclined towards passions…”

Intellect gives one the ability to understand the end result [of various] matters, and madness covers it, [impairing this ability]. Because the intellect of the youth is not complete it causes fickleness and impetuousness. Therefore, Al-Mustafa (Sallahu Alaihi Wa Sallam) cautioned [them] from hastiness and encouraged proceeding with caution.

Another point the scholars mention is that the hadith gives glad tidings to the youth and shows that they should be shown such tolerance and forgiveness that is not shown to older people who are fully mature.

And Allah knows best.
Sources:
Kashful Khifa Vol.: 2, Page: 3-4
Faidhul Qadeer Vol.: 4, Page: 171
Siraajul Muneer Vol.: 2, Page: 341