One of the interpretations of the definite article is what is necessary for a specific task or goal:
I want to write a book, but I don't have the time.
(= time needed to write a book)
I would mow the lawn myself if I had the strength.
(= necessary strength to mow the lawn)
He could be a great manager, but he lacks the initiative and motivation.
(= initiative and motivation needed to become a manager)
We need a bigger house, but we don't have the money right now.
(= the money needed to buy a house; enough money to buy a house)
If you remove the definite article from the above sentences, they are a general statement about a quality these people lack, but not related to any specific goal. The definite article links these qualities with the stated task specifically. For example, in the last sentence, ", but we don't have money right now" implies they don't have money for anything, whereas "the money" refers specifically to the amount needed for a house.