There's a show on TLC called "What Not to Wear." It's not a show we watch on a regular basis, because the subject matter is pretty repetitive and the issues the featured people (mostly women) have are very similar from show to show. But once in a while, for fun, when I'm in the mood for the hosts' personalities and maybe when I'm feeling that it's time to revise or edit part of my life, I tune in.
There are other shows, of course, that are based on the "makeover" concept, ranging from BBC's "How Clean is Your House" to A&E's "Hoarders" to most of the design shows on HGTV. "What Not to Wear" is great because the hosts force the subject both to participate in editing their wardrobe and choosing new pieces, and to engage in a dialogue about what they've been doing and why it isn't working for them. Let's face it, if your dearest friends and family nominate you for a show like this (or if they tease you about how they're going to nominate you) it's a good clue that what you think is working, actually isn't.
The dialogue is the essential part, I think. To have to articulate why you think some manky old coat is "you" really forces you to examine it. Because these hosts don't let people off easily. They push, and nag, and berate if necessary. If they ask you what you want, they also ask, "why do you want that?" And often they add, "You shouldn't want that. It looks awful. Why do you want to look awful?" Once in a while, it's helpful to get that kind of feedback - to engage with someone who cares more about helping you get over yourself than about making you feel good about yourself.
Professional organizers play the same role, and they have the added fun of bringing their "why must you keep this?" dialogue to everything in your space, not just your closet. It's getting easier and easier for me to let go of some things. Other things I am committed to keeping indefinitely, or I keep because they work really well in the space we have. If/when we leave this space, a lot of things are going to be subject to review because they won't necessarily work anywhere else. I just try to be conscious about it.
Pretty much every year I go through the kitchen and my closet to sort out things I haven't used. Books have been the big thing for me this year. How do you choose what to keep? I've boiled it down to education and entertainment. "Entertainment" books I keep until I am pretty sure I won't re-read them again. (Keeping a reading journal helps with this.) "Educational" books are apt to be slowly shuffled out as I get through them, because once I've read and assimilated that information, I'm not really going to need to refer to it in the future, and I won't pick up those same books just for fun.
That said, there is certain subject matter that, if you haven't gotten to it within a year, it's time to pitch it, because it's hopelessly out of date already. In this category I'd place books about diet, general health, etc. I even include books about anatomy here. I've got several myself, and some I know I will refer to in the future, but a couple of the others are beyond what I'm going to need as a part-time fitness professional, especially given that my focus is on dancing.
The truth is, research is constantly advancing, there is new information every year, and most of it is available for free online. Plus, I receive several health/fitness magazines, including the publications of my continued-education providers, and those furnish much more up-to-date information than books can.
Same goes for textbooks and books about finance, investing, etc. Anything that's not being referred to in the here and now should go, because better, more current information is available on the web. Books of this nature tend to be especially big, heavy, badly written, and narcolepsy-inducing: if you're not reading them for their content, you are certainly not going to read them for entertainment.
Travel books? They are useful only when you actually travel. A 2005 edition of "Let's Go Mexico" is not going to be terrifically helpful if you don't go back to Mexico until 2015, because, you know, things change. Cookbooks? Useful only if you actually cook. (And frankly, I've found the Food Network to be more inspiring for my usual style, which is a lot like the competition show "Chopped" - I look in my cabinets, survey the odd collection of items, and try to make something out of them.)
It's important to give yourself permission to get rid of things. Just because you bought it intending to use it and haven't, that doesn't make you a bad person; on the flip side, it doesn't mean the thing still has value. Indeed, it's a bad idea to rely on old information. So if you have several areas of your life that need revising or editing, take a look at the bookshelves first. Remember, the information is out in the world: it doesn't need to be in your home.