Here is a beautiful prayer written by Saint Ignatius of Loyola who was the founder of the Society of Jesus. His Feast is celebrated on July 31st.
Lord, teach me to be generous.
Teach me to serve you as you deserve.
To give and not to count the cost.
To fight and not to heed the wounds.
To toil and not to seek for rest.
To labor and not to ask for reward.
Save that of knowing that I am doing your will.