I think an important thing you hit on is internal vs. external change. You can be an angry cuss, change the city you live in and still be an angry cuss in a new place. External changes will only ever have a moderate impact of how we live our lives if they’re not accompanied by continuous internal changes.
If you’re not satisfied with what you have, no new job, fad diet, possession or relationship is going to fix that. But if you can make small simple changes to your daily life like telling one person each day that you appreciate them, skipping the junk food at the grocery store or buckling down to complete your to-do list at work each day, things will start to go well, guaranteed.