Colossians 3:23-25
And whatsoever ye do, do it heartily, as to the Lord, and not unto men; Knowing that of the Lord ye shall receive the reward of the inheritance: for ye serve the Lord Christ. But He that doeth wrong shall receive for the wrong which He hath done: and there is no respect of persons.
The state of your spirit conditions the things around you. Your joyful state, will reflect on the things around you and in the things you do. You must maintain a joyful atmosphere all the time. It increases your productivity.