What is the difference between sustenance (rizq) and divine success (tawfiq), and what is the relationship between them? Is a person's sustenance predetermined, such that they cannot exceed it no matter how hard they strive? And does something known as an "obstacle" (al-arid) exist that stands in their way?

Sustenance (rizq) is what Allah bestows upon His servant, be it wealth or other provisions. It is predetermined in Allah's knowledge; it neither increases nor decreases. As for divine success (tawfiq), it is that Allah does not abandon you to your own devices. The greatest cause for a lack of divine success is committing sins and transgressions, as Allah Almighty says: "And whatever strikes you of disaster - it is because of what your hands have earned, and He pardons much." And He says: "Corruption has appeared on land and sea by [reason of] what the hands of people have earned so He may let them taste part of [the consequence of] what they have done that perhaps they will return." The Prophet, peace and blessings be upon him, said: "Indeed, a man may be deprived of sustenance due to a sin he commits." One must adopt the means [to achieve goals] while believing that these means do not yield results except by Allah's permission. There is no such thing as an 'obstacle' (al-arid) that stands in one's way, and believing this is a form of forbidden pessimism (tashaa'um), for the Prophet, peace and blessings be upon him, said: "Omens are polytheism (shirk)."