To start with getting older doesn't have to mean diminishing health. Some people do sadly end up with medical problems, but many of the problems of old age are self inflicted. Obesity, lack of exercise, poor diet - and a good diet doesn't require fancy fruit and veg. Cabbages, carrots and apples are just as good.
So start with a positive attitude to your health so, if you are overweight inactive or eating badly, start to change that. There is nothing so life enhancing as a good walk, walk briskly, look around you. The immediate environment is itneresting even in big cities.
Then find something to do that is useful and fulfilling and that you enjoy anything from joining a knit and natter group, to volunteering to studying a subject to interest you.
At the end of the day only you can help yourself - and you can.