Turning 46

Last year I turned 46.  This has been the hardest birthday, at least mentally thus far.  Why has it been so hard?  I don't know.  Maybe the death of a parent and sister in the last two years has something to do with it.  Maybe the realization that I am not getting any younger.  Maybe the fact that I am not as spry as I used to be.   Why is it hard?   I don't know.  Any suggestions?