I can’t define better. But I can tell you who can. The people around you that you trust can tell you when you’re better and when you’re not. They will not tell you you are better drunk or on meth. (unless they are also drunk and on meth - that’s codependency, not trust).

If you’re really, really lucky you will find a life partner who knows you top to bottom and will tell you when you’re better, and be patient enough with you when you’re worse to really know the difference.