Mission, Purpose and Passion.
The last of these is PASSION. So if you Mission is your overarching architecture of the building, and the purpose is what you are doing inside that building, then PASSION is the electricity that runs it.
Mission and Purpose without PASSION is like having the logs in the fireplace and not having a match to get it started.
PASSION is the energy that's needed to move your Mission forward, because when all three are present, and they are all in alignment ... it really is magic.
Work becomes easy, obstacles melt away, challenges become opportunities, and work is something you do because it is your life, not because it is your job.
When I was working at the Health Services, I thought being a clinical nurse practitioner would be terrific. My personal Mission of serving those in need was present, my Purpose of improving the health of those in served was being met, but I didn't have any PASSION. There was no spark to ignite my flame of tenacity to achieve my Mission. Perhaps I had no PASSION for my work because I know those kids would be fine without me, their sore throats would go away, their tummy aches would be resolved, and I would not have made any impact in their life.
You are making an imact in people's lives.
Steve Jobs said at his commencement speech to Stamford, "Your work is going to fill a large part of your life, and the only way to be truly satisfied, is to do the work you believe it truly great. And the only way to do great work, is to LOVE what you do! If you haven't found it yet, keep looking. Don't settle. As with all matters of the heart ... you'll know it when you find it."