Finding product-market fit (PMF) is a complex, iterative process crucial for startup success, as illustrated by the experiences of former Mixpanel PM Vlado Hruda and the failures of companies like Quibi and Juicero. The journey to PMF involves understanding and meeting market needs through data-driven insights, rather than merely having an innovative idea or substantial funding. Methods like the Sean Ellis Test and Net Promoter Score (NPS) are useful for gauging PMF, but the most effective approach involves using product analytics to improve user retention by identifying "aha" and "habit" moments that encourage long-term user engagement. Mixpanel's experience demonstrates how guiding users toward actions that enhance their experience can significantly impact retention rates, ultimately achieving PMF. For venture capitalists, PMF is a critical determinant in funding decisions, underscoring its importance in the growth and sustainability of startups.