What is the meaning of the phrase "What is sufficient for the individual is not sufficient for the group"?

This statement is correct and means that an individual may adopt a stricter approach in some matters as a precaution or out of piety, but severity should not be their constant practice, as severity is rejected and leads to neglect. If an individual broadens this, it does not apply to the community, so they should not impose severity upon people. The evidence for this is abundant, including the Prophet's (peace be upon him) saying: "If one of you leads people in prayer, he should lighten it, and if he prays by himself, he may prolong it as much as he wishes." The Messenger of Allah (peace be upon him) used to pray at night until his feet cracked, but when he prayed with people, he lightened it. Among the statements of scholars on this meaning is Al-Jassas's commentary when interpreting Allah's saying: "Allah does not intend to make any difficulty for you."