What's the best way to make a difficult choice?

I am looking for ways I can make a decision that will greatly affect my life. I’ve never been faced with a decision like this and I need some strategies.

It involves my job, my upcoming 36th birthday, and me being in a serious funk and desperately wanting to change my life. My concerns are my personal well-being and my obligations to others.

How would you make such a life changing decision. I don’t even know how to begin.