Jane's answer... The short answer is: keep the clothes that...
Fit well
Flatter your body shape
Are in colors that suit you
Are contemporary
Are in good condtion
Are suitable for your lifestyle and
Suit your personality
It's a good idea to review your wardrobe at least twice a year, just after the change of fashion seasons. For more about how to do this take a look at my wardrobe de-tox and planning articles here.