I can't really tell you what will help you, but I can offer my approach:

I don't know if I suffer from depression because I don't know what to compare it against. I am aging. I can not do what I used to do. I have an irregular heartbeat that worries me slightly. If(when) I can no longer ride, I plan to walk regularly. Walking can be an amazingly useful exercise (others have told me) for conditioning, weight loss, and stress relief. I almost feel a relief that walking might still be my savior when riding is no longer possible.

Regarding worrying about keeling over in a bad spot, I try to just do the things I enjoy. If my time comes, I would prefer to be doing what I love. I know that sounds shallow, but I don't know how else to approach my own vulnerabilities.