I totally understand where you are coming from.
What has been REALLY working for me is exercise. Without it, you will lose energy, become depressed, and lose your motivation. But you HAVE to do something that you like – if you find yourself dreading it, you will not exercise and feel even worse.
I love the forest and live in an area with lots of beautiful trails in the Pacific Northwest. I also love to dance, so I take classes three times a week. I had a foot injury that kept me from exercising for a year, and I felt terrible. I had to start from scratch to get my endurance back up, and believe me, it sucked…I could barely walk out of class, was totally wobbly and …ewww. But I just kept at it, and now I see a huge improvement (within a few months!) in my fitness level, my weight, and my overall outlook on life. I have A LOT more energy now.
It is REALLY hard to start and continue, but the results will be SOOO worth it! Age has nothing to do with it. (Although it does take a bit longer to get fit.)