I was caused to remember this pop-therapy canard because Anne Hathaway's character Maggie Murdock uses it in Love and Other Drugs, which is a better movie than you think it is. Sure it has sentimental moments, and the whole ending is silly, but there's also the short scene where the guy married to a woman with advanced Parkinson's says "Go back to your hotel room, pack your bags and leave. Find yourself a healthy woman to live with. I love my wife, but I wouldn't do it over again." I'm betting there were husbands in the cinemas all over the world who murmured "Allelujha' and then went back to caring for their wives.
Anyway, there's a scene where Maggie Murdock (did I mention I really, really like Anne Hathaway? No? Well, now you know) asks boyfriend (Jake Gyllenhaal) to name four good things about himself. He can't, of course, and Murdock does a sympathy number on his terrible competitive family. Because of course, there are any number of things to like about his character's character. But that's not the point.
The "four good things" thing is a therapeutic one-two. It's intended to prove to you just how lousy your self-esteem is, just how badly you got worked over, and just how much work you need to do - at £50+ an hour - to get better. I mean, how badly beaten up do you have to be not to know four good things about yourself?
You don't have to have any psychic bruises to be unable to roll off four good things about yourself. Being able to do so off pat comes across as a party trick. Being able to do so after a bit of thought might suggest decent self-esteem. It's what the therapist does with the answer that's the real blow. Any answer can be dismissed with something along the lines of "is that all?", or "those things aren't about you, they're about your roles at work and at home. What about you?", or "those are all about performance, aren't they? What about who you are?" (After you've said you're an award-winning photographer, can run the Marathon in under four hours, cook to Michelin One-Star standards and coach deprived children in English during your lunch-hours.)
It's a silly question. As daft as naming four good things about your car. ("I don't know: the tyres?") The car works as it should, and for modern cars that's a given not a thing of wonder. You are a regular guy, and regular-guy-ness is a given. It's not remarkable. Of course you can't name four good things about yourself, let alone four that a half-competent therapist can't turn against you in two minutes.
However, you shouldn't be able to name four terrible things about yourself easily either: if you can, someone did really effective emotional sabotage on you. And that needs working on.
What you should be able to do is name four things about yourself that you're improving right now. (My bench press / upper body; my heart-lung and legs by interval training on the treadmill; learning LAtEk; my 2013 work and casual look. Since you asked.) You should be able to do this because you are not a self-satisfied SWPL and there are always things you can improve or change.
If you ever get asked that question, in earnest, by anyone, be polite and give them the answers to "tell me four things you're working on right now". Then thank them for their time and delete their contact details. Because they are either a new-age manipulator, or an idiot who thinks it's a sensible question, or overly impressionable. None of those are people you want to spend time with. (Okay, if she's pretty and available, then one night. But that's all. Maybe two. But no more.)