Muḥāsaba: Taking account of yourself
Muhasaba means going through your own accounts, and al-Ghazali gave it a long stretch of the Revival. A person doing this stops after years of hard work and asks flatly what it all came to. The honest total can land heavy, and hearing it from yourself carries a weight that no warning from anyone else ever has.
Ṭūl al-amal: Expecting endless time
Al-Ghazali writes about tul al-amal, laying plans as if the years ahead were unlimited. Expecting more time is what keeps a person building: one more project, one more season, with the payoff always sitting a little ahead. The chase has no finish line inside it, so no amount of finishing things ever quiets it.
Zuhd: Doing without
Zuhd means holding what you own loosely, and the early Sufis treated it as a first step rather than a summit. Someone who has just watched their achievements come out weightless will often grab harder or quit altogether. A third road stays open, where the work and the house and the money remain, and the demand that they fill you up quietly drops away.
Ikhlāṣ: Sincerity
Ikhlas means acting for God alone, with no eye on the return, and al-Ghazali writes at length on how mixed our reasons usually are. Work done for the name, the standing, or the proof that we mattered gets paid in exactly those things, and it thins out when they do. A full life can come out empty for that reason alone.
Everything other than God is empty: only one thing holds its weight
An old Arab poet wrote that line, the Prophet praised it above all other poetry, and al-Ghazali made it the center of the Niche of Lights. The claim is not that the work was worthless, but that nothing standing on its own was ever going to hold. A person who finds their own results hollow has seen something correctly, and what stays standing after that is God.