What is there left for me to live for at 66?

Call 1-800-272-8255. You don't have any answer(s) right now. But that doesn't mean that you won't come up with some. Talk to someone who will try to understand how you feel & what's going on for you. To get started, call 1-800-273-8255. This is literally a lifeline for people who can't come up with reasons to live. You don't need to be feeling suicidal to call.
Plenty. Age 66 is now a very common age. Assuming that health is not an issue and that you are in crisis like living on the street, there are plenty of things possible. You can engage in activities to help your fellow humans, volunteer for charities, get politically active, get serious about your church, travel, take courses - the list goes on and on.