काममय एवायं पुरुष इति स यथाकामो भवति तत्क्रतुर्भिवति ।
यत्क्रतुर्भवति तत्कर्म कुरुते यत्कर्म कुरुते तदभिसंपद्यते ॥
The individual person is made of desire. As is your desire, so is your motivation. As is your motivation, so is the action (karma) you perform. As is your action, so is what you will eventually attain and become.
~ Chhandogya Upanishad
Desire is the root of the mind and the source of its motivation, willpower, imagination, effort and seeking. As is your desire, so does your mind function in the pursuit of that desire, whether ordinary desires for enjoyment or higher wishes, such as the aspiration to gain liberation (Moksha) or Self-realization.
Desire-based motivation (kama-kratu) is the basis of our actions and determines our karmas and the fruit of our actions. Yet we seldom are aware of the complications that our desires can lead to as we pursue them, or the long term karmas we are creating.
Vedic Counseling Advice
Be very careful what you wish for, as you may get it, not in the form you wish for but in the nature of the desire and the actions that you set in motion. Do not trust your mind to always desire what is best for you, what brings you lasting happiness, what helps others or benefits the world.
Note that the more desires you have, the more your inability to achieve them, as you may lack the focus, energy and determination to fully achieve any of them. To reach the highest you must have a one-pointed mind, with a steady aspiration to reach the immutable truth. That is the Upanishadic way of Self-realization.
To understand and transcend our karma, we must change the nature of our desires and motivations accordingly. This is to make our sadhana or inner spiritual practice our main action and motivation in life, and all other desires must be subordinated to it. To achieve the highest, we must value it over all else and dedicate all our time and efforts to achieve it. This puts us in contact with our eternal and infinite Self (Atman) in which everything is possible.