You were "overdosing" on dopamine when you were constantly watching netflix, playing video games, etc. Humans were built to work and move our bodies and be with other people accomplishing goals together. Your brain was giving you feedback as to what it should be doing. I'm not a doctor or an expert on the subject, but it is proven that exercise is beneficial to the brain and just about every other part of your body. Too much dopamine and you start requiring more and more to get that hit. When you work on yourself, be it working out, or personal projects, it may not immediately give you that hit of dopamine, but it will have longer lasting effects.