If you look at any major corporation, church, organization or small business no doubt you'll find that they have a mission statement. This statement is in place not only to inform patrons of the mission of the company, but also to keep the company on track and moving towards that goal. The company will likely try to eliminate things that keep it from that goal, and will do things that help it towards that goal.
What's interesting is that while most CEOs, church leaders, and small business owners could almost certainly tell you off the top of their heads what their business' mission statement is, it's unlikely that they've ever sat down and created a mission statement for their own lives. In fact, most people don't stop to think about what they want as a mission statement for their lives. Developing a personal mission statement is basically "connecting with your own unique purpose and the profound satisfaction that comes from fulfilling it" (Stephen Covey in First Things First). A mission statement doesn't have to be career oriented at all, nor does it have to encompass your entire life. Your high school self will likely have a different mission statement than your self who is married or has kids. Life circumstances will definitely affect what your mission statement looks like, however I think there are also parts of your mission statement that should reflect your core desires and purpose. Your mission statement will undoubtedly change and evolve as you change and grow. Continue to evaluate it and make changes as you need to.
I've found a couple sites that help you to build a mission statement if you're having trouble boiling it down (I sure did!). Franklin Covey has a great 10 step mission statement builder. I used this one and liked it a lot. The end mission statement is very long, but it helped me to define my mission and out of their questions I was able to boil down my 1-3 sentence statement. This article also has a great 5 step plan for helping figure out your personal mission statement. If you google "personal mission statement" many useful links come up and you can peruse them to find which ones you think are helpful.
Here's what I've got for my personal mission statement at this point in time:
My life's journey is to inspire and give others the tools and resources to become the most whole person they can be, stretching them out of their fear and into growth and personal wholeness.
I will stop listening to the limits I place upon myself and move towards my goals with enthusiasm and passion.
I will cultivate my adventurous spirit.
I will bring beauty and inspiration into the world.
I will do my best to enable others to do the same.
I will cut out the parts of my life which keep me from doing the above.
If you're having trouble figuring out how to word your mission statement here's a site which gives a few examples. There's really not a wrong way to do it, but it's nice to see how others have gone about it.
If you feel like it, share your mission statement on the forum! It would be inspiring to read everyone's personal mission statements!