All Muslims, whether young or old, must prepare themselves for the Hereafter (akhira). They must be ready for when Allah will account everyone for everything they did in this world. Imam al-Ghazali through this quote is alerting and advising that before Allah accounts you, you should account yourself and prepare yourself for that Day by preparing now through learning about Islam and its subjects, practicing it, delivering it to others, sharing it and keeping firmly on it.