Start doing Cardio
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I guarantee you, you'll feel better. I'm sure there are quite a few people here who do not exercise. Well, you should start. This is a reminder. The first thing you should remember about cardio is, you'll always feel better and have more energy AFTER you're done. So having the excuse, "I'm too tired to do cardio." Is just illogical. You do cardio to get energy. It feels so good when you're done. Not only do you emotionally feel better, but you'll think more clearly as well. Your blood gets moving and it pumps through your entire body it's great. It'll also make you live longer.
For me, I started by running around on this circle in the woods. There was a mile turn around near where I lived. There were no houses, and maybe 3 small warehouses/office buildings with a huge storage lot for cars. No one would drive up there and the air was super clean. That's the absolute best. Your lungs are going to get tired out, every muscle gets a work out, and it just feels awesome. Don't be discouraged, at first you might only be able to go a quarter mile, but keep at it and you'll rapidly get better.
If you're overweight, you'll want to do something like a bicycle/bicycle machine or elliptical. Running when you're obese or overweight is going to hurt your joints and you could do some serious damage to them.