Imam Hasan Al-Basri rahimullah, was asked one day the secret behind his self discipline and moderation. Imam Al-Bari mentioned four things in reply:
1. I believe that my sustenance will never be hijacked by anybody (so I work to attain it).
2. I know that a work that is mine must be performed by me, so I do not decrease my efforts in performing it.
3. I believe that my Lord is Omnipresent (watching me), so I do not like Him seeing me committing sins.
4, I know that death is somewhere waiting for me, so I prepare for it (through good deeds).
As we go about our day to day work we should seek to do all of the above and we also seek challenge and achievement, these are 2 of the basic human needs. If we are not achieving or feel fulfilled it is harder to keep ourselves motivated.