How can someone integrate the Buddhist philosophy on life's purpose into daily life?

The question 'What is the purpose of life? ' has been asked before. What I understood is that if I were to set a purpose to life, once I achieve my goal, life becomes meaning less. There is no single thought great enough to spend an entire lifetime. So, life has no intrinsic meaning. In everyday life, we try to plan things. Setting goals provide clarity about what exactly to do, what's important and what's not. Reaching goals help building self-confidence and motivates to move forward. It also helps to work efficiently while dealing with big tasks (Makes big tasks into smaller, more manageable units, Helps good decision making that are inline with the final goal). Both sound reasonable to me but they also seem contradictory. Then how should a lay man approach his life to be productive and at the same time seek liberation from the sufferings of samsara?