How does faith lead to a Muslim's attainment of inner balance?

Faith in Allah necessitates submission to His divine decree (qada) and destiny (qadar), and that everything occurring in the universe is written with Him. Allah Almighty said: (No disaster strikes upon the earth or among yourselves except that it is in a register before We create it – indeed that, for Allah, is easy In order that you not despair over what has eluded you, nor exult [in pride] over what He has granted you) and (No disaster strikes except by permission of Allah. And whoever believes in Allah – He will guide his heart). The believer seeks reward for calamities to expiate sins, for everything that afflicts a Muslim of harm, Allah expiates some of his sins thereby. Worrying about future calamities leads to a loss of inner balance, whereas faith leads to balance.