Well said Falconbird particulary,"keeping busy is a solution." I heard a quote once roughly saying, "life is 10% what happens and 90% how you deal with it," which I believe is true.
I have been on my own for 8 or 9 years, left a husband in Spain 6 years ago and have no idea where he is now. My two sons from a first marriage live abroad, so I rarely see them and obviously they cannot offer any support. I moved here 6 years ago having only one friend in the area but now I am happy to say, I cannot walk down the high street without meeting two or three of my new friends. This is because, like you, I joined as many activities as I felt able to participate in, and I haven't looked back.
Of course, I am concerned about what will happen as I get older and possibly infirm, but it doesn't do to dwell on that, the worse thing is to sit moping and feeling sorry for yourself. I volunteer in a charity shop as one of my activities and enjoy nothing better than the interaction that brings with the lovely customers. Lots of other things too, including online courses which provide an ongoing challenge which I think is important, the garden, keep fit, walking group, they all bring their rewards.
So there is hope in old age if you make the effort, it is up to, you, no one will do it for you, and very proud you will be in your independence and achievements.
Blimey, this is the longest post I have ever written, I will get off my soap box now. 