Colossians 3:23-24

Whatever you do, work from the soul (that is, put your very best effort), as for the Lord and not for men, knowing that it is from the Lord (not from men) that you will receive the inheritance which is your reward. It is the Lord Christ whom you (actually) serve.

When we realize we are not living this life just for ourselves but are serving the Lord, our perspective changes. How much effort do we put into something if we are angry at the person we are doing it for? But if we remind ourselves that we are here working for God as His representative, we are more motivated to excel.