Some random ideas that I think could help you to find what you're missing:
*Build something, could be a tiny house in your garden, house on a tree, greenhouse or even a forniture.
*Get a dog, it will force you to go out and walk every day few times a day. Training a dog is a good challenge and it come with some rewards.
*Volunteer in any NGO, helping others it is a good way to help you.
*Find love. with the right partner everything works out better.
*Grow some plants.
*Do some exercise. Running is a mental challenge, try it.