Use your youth for the sake of God. The fruits will bear in this life and the hereafter.
Ibn Rajab al Hambali (may Allah have mercy on him) said:
“Whoever is mindful of Allah when he is young and strong, Allah will take care of him when he is old and has become weak, and will bless him with good hearing, eyesight, strength and intellect. One of the scholars who lived beyond the age of one hundred years and enjoyed good strength and reasoning jumped up in a lively manner one day, and was asked about that. He said: ‘I kept these physical faculties from sin when i was young, and Allah has preserved them for me now that I am old.’ The opposite also applies. One of the Salaf saw an old man begging from people and said: ‘ This is a weak man who ignored Allah when he was young. So, Allah is ignoring him now that he has grown old.'”
(Jami’ al-ulum wal Hikam)