Stop regretting the past, stop worrying about the future (85% of daily worries never happen anyway), and stop looking for happiness from other people. Happiness is internal, not something someone else can give you.
Chapters
Three things that you should stop doing immediately if you want to be happier. Number one, you have to stop regretting the past. There's nothing you can do about it. Don't forget the past. You can learn from it and get better from it. So you don't make the same mistakes. But you got to stop regretting the past. Number two is stop worrying about the future. Psychologists have found that 85% of what you worry about on a daily basis will never happen. That's a waste of your energy. That's a waste of your time. And number three, stop looking for your happiness in other people. Other people cannot make make you happy. It is absolutely impossible. Happiness is 100% an inside job.