What is a thought?
Dictionary.com will say it is the product of mental activity; that which one thinks. MIT says: “They’re really just electro-chemical reactions—but the number and complexity of these reactions make them hard to fully understand…”
You have to learn to manage your thoughts. If you set a new habit go to the gym, weigh XX that’s great but if all your thoughts revolve around “I’m fat, I’ll never be a fit person, I don’t like the gym” then you can see you’re going to have a hard time reaching your goal. So perhaps your first habit should be learning to have more helpful thoughts.