One of the main challenges was ensuring secure user authentication while providing a personalized dashboard. Implementing JWT-based authentication allowed us to secure user sessions, but we ran into issues managing tokens across frontend and backend, especially when trying to keep users logged in across different pages. We overcame this by utilizing local storage for token persistence and middleware functions in the backend to validate each request. Another hurdle was making the dashboard dynamic so that users could see personalized data, such as their BMI, workout stats, and goals, in real time. Chart.js helped us display user-specific metrics visually.