Training is in red for danger. Don’t just go out there and run with no experience! You’ll be sidelined and demotivated in no time by shin splints, plantar fasciitis, ileo-tibial band syndrome, or worse. Study your chosen sport, talk to those who already do it and ask them about the challenges they faced, and enter it cautiously at first. In fact, the best way to start most land sports is conditioning through long walks.
To maintain a healthy body and mind, undertake a gentle process of relentless learning. This will become a way of life after a while. NEVER think that it is too late or you are too old to get in shape. Your mind and body respond to load, so load them up wisely and as a life style choice.
Finally, I recommend that you read The Brain That Changes Itself, by Norman Doidge. This is the best self-help book I ever read. It will convince you that change is possible and within your reach.
Have fun exploring the response of your mind-body to exercise, and remember, a life without risk is no life at all.
Having scratched the surface of this topic, I wish you well, and happy trails.