be less lazy

This might be something that sounds simple to change but for me it’s not and I have been fighting it for years! I don’t want to be lazy but it’s more about me being TIRED all the time. After awhile I thought maybe me being tired was a medical condition or I had low iron. I went to the doctor and she checked me out and told me I was fine and healthy.
After that I was reading in a book that if you start to be lazy and less active your body gets used to that so when you try and start being active again your body resists because it is not used to it. This is something I am going to have to work on one step at a time.