Grandmothering and the bittersweetness of life

Yesterday my oldest grandchild graduated from preschool.  I was crying a little as soon as they started to play the Grand March (so cute for those who are so little).  That was good though so that my camera eyes were ready when Jonathan began his march.  I cry a lot around the grandchildren issues but I think that my crying personifies the definition of bittersweet = arousing pleasure tinged with sadness or pain.  So tears are cried out of happiness and pride about the little one's advances but there is also that sense that time is moving on, the grands are moving on, things are going to change.  Ahhh, there's the rub: change.  They change who and what they know, make new friends and join activities that take their time.  They move to new schools so there's the possibility of seeing them less frequently.  Their "free time" for spending times w/ the g-parents seems like a smaller window of opportunity.  So I cry.  We finish a vacation where we've taken one of them (soon to be more), and I cry.  They are here playing in the yard pretending to mow the lawn, rake, and shovel, and I'm maudlin when they leave.  That's right: self-pity takes over. Why does change, growth sometimes engender that self-pitying feeling?  I can grow too; my life will change with theirs.  But, my life is changing toward the end, and while so is theirs, they have so much more left!  Every graduation that they each make is a "graduation" for me toward being older and my life changing.
Thank God I am healthy and active and plan to continue to be so.  For example, our oldest grandson is interested in rock climbing so I bought myself new climbing shoes yesterday.  Haven't climbed in at least 15 years but I feel a revitalization, a renewal.  That is how I prefer to look at the passing of time with my grands - they are allowing me to learn new things, practice new skills (like how to use all the new fangled technology out there), and relive experiences that I treasure and now show them (skiing, camping, mt biking, general exploration of the world!)  So I get a redo in many ways.
I guess that growth is tough and certainly change creates angst in many unless you are firmly entrenched in that idea that change is good; nothing good happens in a vacuum.  I remind myself that 2012 especially is about change: the year of the Yang Water Dragon.  Part of the power of this year is having the ability to flow with change - one can miss opportunities if you are unwilling to change.  Will, determination, ability to flow will all lead to abundance.  All these grandkids = abundance!!!