Is your eyesight and general health still good enough to let you ride a bike? Both two wheeled bikes and trikes and cargo bikes can easily be found with an electric motor these days.
And if walking is still relatively easy, then instead of just popping up to the shops etc in the car, walk there. I use a medium sized back-pack to carry shopping in, or time my shopping trip, so I walk up to the shops and take the bus home. You may prefer a shopping basket on wheels,
If you live far out in the country with no bus service, not being able to drive may mean ultimately that you have to move.
Find out though what a taxi would cost to your doctor's, the shops etc, and whether there are lower rates for the elderly or those who legally may not drive. Citizen's advice ought to be able to tell you what options you have.
Have you a friend or neighbour who might help out? If so, discuss to start with how much help that person is willing to provide - it is better to start with a mutual decision that she or he takes you shopping at the start of each month and you contribute to the petrol bill, or that the person will only help out with health-related appointments, than to feel. or be made to feel later that you are placing unreasonable strain upon the friendship.
Most supermarkets deliver food these days.
Take a look at what it actually costs on an annual basis to run a car, fuel, maintance, MOT, insurance all adds up to an amount you can take a fair amount of taxis for.
None of us likes being forced to realise that there are things we can no longer do, legally, or without risking our own or more importantly others' safety, but we may have to accept these limitations as we age and find solutions.