Why Can't I Change My Behavior?

In today's episode, Dr. Lisle discusses the following question: Do you have any tips for getting yourself to do the hard things you know you should do? I am a voracious consumer of self-improvement content. I truly believe in the science and superiority of the whole food plant-based diet, in the importance of regular exercise for physical and mental health, and in the benefit of productivity and life-improvement. I have things that I know would absolutely improve my life in the long run but I cannot seem to make myself do these things, even though I am high in conscientiousness. It's as if I keep convincing myself I can just "slip on by" being lazy. It's a pattern that has followed me all my life - I'm quite smart and always got good grades but I've only put in the effort to do well rather than extraordinary well like I could have, even though I know this would be of great benefit to my life in the long-run. I just don't know what to do with myself anymore. I'm in my mid-20s and obese, lonely, depressed, addicted to technology, and performing far below what I could be in life. How do I get myself to do the things that I know will make myself more happy and increase my competitiveness in society?