How can one renew their intention daily, and what are the signs of sincerity in working for Allah Almighty?

In Islamic law, niyyah (definition) (intention) is the heart's inclination towards what it perceives as beneficial or useful, whether to gain a benefit or ward off harm. Its place is in the heart. It is a condition for the validity of acts of worship, based on the Prophet's (peace be upon him) saying: "Deeds are only by intentions." The intention serves to distinguish acts of worship from habits, and to distinguish some acts of worship from others—this is what jurists are concerned with. It also serves to distinguish the intended and the worshipped (sincerity), which means that the worship is intended for the sake of Allah Almighty alone—this is what those concerned with spiritual purification focus on. The intention does not need to be renewed every day; rather, it is required when undertaking each action. There is no specific formula for it; it suffices for one to intend in their heart, when praying Dhuhr, that it is the obligatory Dhuhr prayer and that it is for Allah. It is commendable to improve one's intention in ordinary matters so as to be rewarded for them, such as sleeping and eating with the intention of strengthening oneself for obedience to Allah.