Background and Objectives: The impact of coronavirus disease 2019 (COVID-19) goes beyond the consequences of the infectious disease, especially as the measures taken to prevent the spread of the virus have had a very profound impact on people’s social relationships and everyday lives. Several studies have investigated these effects, but there is a lack of longitudinal studies in Central Europe. Objective: The aim of our study was to observe changes in well-being, loneliness, and suicidal behaviour before, during, and after the COVID-19 pandemic using the same population-based cohort. Materials and Methods: A representative sample of 440 participants completed online questionnaires at four time points: 2019 (wave 0), 2021 (wave 1), 2022 (wave 2), and 2023 (wave 3). Results: The results show significant changes in the levels of well-being and loneliness over these periods. In particular, both social and emotional loneliness increased during the pandemic, while emotional loneliness increased to a greater extent without further decreases. Well-being appeared to increase after pandemic-related restrictions diminished but decreased again one year later. No significant changes concerning suicidal ideation were observed. Conclusions: Our study suggests that the COVID-19 pandemic changed the way in which people perceive their well-being and especially their relationships with others. From the data, we can conclude that people’s worldview is now lonelier than before the pandemic.