I have been following this plan for getting rid of clothes.
First, divide into categories:
1. Wear all the time, love. OR need for work and wear all the time.
2. Doesn't fit or looks like crap or just looks...bleh and makes me unhappy when I wear it.
3. Haven't worn in years. (interview suit excluded)
4. Sentimental value. (such as concert tees, dresses worn for special events)
Category one I keep.
Category two I give away, reminding myself someone else will then get to use it; another way is to offer really nice stuff (which is its own kind of attachment) to people I know before donating it somewhere. Sometimes I forget I've given these things away, because I never thought of them while I had them.
Category three I revisit - maybe give the garments another try, which leads either to redicovery and transfer to category one or realizing why I stopped wearing it, so I can give it away.
Category four I re-examine periodically, to see if the need to keep has diminished. In some cases it has, and I give away.
Anything that needs repair, if I don't have it repaired/repair it myself within a month, out it goes. Ditto drycleaning that's been lying around.
A tricky category for me is choir clothes - I have a wide range of those, all black, but in different weights for different weathers, and different ranges of formality. They're sort of subject to the above rules, with the exception that I will keep them a little longer without wearing, just in case. It's a weak spot, for me!