Make a conscious effort to stand for an hour at a time when available seating would be a more logical option. Challenge yourself, and keep track of how long you last. Even if you are physically capable of doing this challenge, your mind may trick you and lead to your doom.
Mine did me after 11 minutes. I'm trying again.
(Here's a tip: Get your computer up off your table or desk by propping it on a banker's box or shoebox, or two, depending on your height).