Again, a very powerful knowledge element from the Bhagavad Gita :

 (2.46)  One has the ability and privilege to do one's respective duty, but has no control over the results. The fruits of work should not be the motive. Also, one should never remain inactive.

When you do anything with most of your attention spent on how the results will be, then you split between two things. You are split between the present moment and the future. Instead of paying full attention to what you are doing, you are constantly worrying about what the results will be.

To be truly happy, you will need to be fully aware of what you are doing and not dilute the energy spent on the activity worrying about the results.