Ageing with difficulty

One positive thing about aging is that you are meant to become more tolerant, wiser and careful.  But it does not always work that way.  Running up and down tiled wet stairs is a case in point.  Which ended in a spectacular fall landing hard on my posterior and being quite painful.  All this because we were looking after our grandchildren - not that they are to blame - it is just that I find it difficult not to run or do things that maybe I should no longer do.
Every time somebody mentions the "Golden Years" which are a way your later years in life seem to be described I want to scream.  Waking up with little aches and pains here and there, slowing down, not being able to do as much as you would like to do, is that so great?  I ask you.  Looking after the grandchildren is a wonderful experience and I would not miss it, but afterwards I am exhausted.  Nobody prepares you for this. 
Looking around me when I go shopping I see a lot of elderly people and I am terrified to start looking that way.  They seem to be so resigned, so slow, bent backs, shuffling, hearing aids, walking sticks, not that there is anything wrong with that in your old age, but how can I escape that?  Any suggestions?  Apart from a glass or two of wine which seems to help us!