Haggai is written after the Jews return from captivity in Babylon. You read about this time in Ezra and Nehemiah. The people return to a destroyed city and are rebuilding it. Unfortunately, they put a higher priority on building nice homes for themselves than on rebuilding God’s temple. Haggai tells them God is going to do great things in the future, and they need to rebuild the temple to be a part of it.
Placing our own comfort above our relationship with God is something that can happen at any time for anyone. Like it was for the Jews, we prevent ourselves from being part of what God is doing.