Complexity becomes dangerous when nobody can explain the whole system anymore.

A system that exceeds anyone’s comprehension has crossed an important line. From that point, changes are made hopefully rather than knowingly, failures cannot be predicted, and nobody can say what a modification will touch. That is true of software, organizations, finances, and households. The danger is not the size but the loss of a complete picture.

Ask whether anyone could describe the whole of the thing you depend on. If not, either simplify it or write down enough that the picture exists somewhere. Comprehensibility is worth protecting deliberately.