Or as referred to more recently... Finding Your Why.
See Simon Sinek at /www.ted.com/talks/simon_sinek_how_great_leaders_inspire_action
While it may take time to fully express your values, it’s important to start with whatever you can do now. By reviewing your life’s peak experiences and defining moments you can see if you can add these back in your life on a more regular basis.
The reality is that you may not be able to make money from your passions, but that doesn’t mean that they should be pursued and aligned with core values.
It may be that this can become a gift you return to the community through voluntary or other activities.
It's also a way to ensure that your values are defined to be able to articulate these to ensure they are compatible with potential employers.
Check out the image to help figure our your passion: