Can Our LIfe Purpose Change?

I was at church this morning and our priest gave a really good homily on discovering our soul purpose.  He said that our life purpose can change.  As long as we're being good people and trying our best each day, then we're fulfilling our life purpose.  My priest explained that he began life as a bull rider, then joined the military and then received the calling to the priesthood.  He said in all those careers he's been fulfilling God's purpose.  I liked the thought of that.  Gone are the days of the thirty year career, of seeking the one thing that will forever fulfill you.  We are here to do many things, to allow God to speak and act through us in a myriad of ways.  I know when I became a teacher, I thought for sure I'd found my calling.  I was so happy in the classroom for many, many years.  But then I received the calling to do this work, and I was so terrified.  How could I leave my safe, secure job that I loved so much?  Now, of course, I'm happy I followed that calling.  I think that my cancer diagnosis might be calling me to something else, too, but I'm not sure what yet.  All I know is that whatever it is, I'll always try to make sure I'm following God's will.  My mantra each day is this: God use me to do your will.

I hope if any of you reading this are afraid right now to take that leap of faith, to leave a job or start something new, that you'll remember how God leads us in the darkest times of our life.  There really is always a rhyme and reason to the tragedies and triumphs of our lives.  All we have to do is surrender to God's will, ask to fulfill our purpose here and follow the signs that will come to us through inner nudgings, suggestions from friends, dreams and coincidences.  These signs form the path that leads us to our next life purpose.

"God has created me to do Him some definite service. He has committed some work to me which He has not committed to another. I have my mission. I may never know it in this life, but I shall be told it in the next. I am a link in a chain, a bond of connection between persons.
He has not created me for naught. I shall do good; I shall do His work.
Therefore, I will trust Him, whatever I am, I can never be thrown away. If I am in sickness, my sickness may serve Him, in perplexity, my perplexity may serve Him. If I am in sorrow, my sorrow may serve Him. He does nothing in vain. He knows what He is about. He may take away my friends. He may throw me among strangers. He may make me feel desolate, make my spirits sink, hide my future from me. Still, He knows what He is about.” 
― John Henry Newman