"I like to say I'm on a wheelchair, not in a wheelchair. 'In' sounds like you are confined to it . . . like the wheelchair owns you. If you're on it, you're just kind of riding it."
When people insist that you must define yourself by what you can't do instead of what you can do, tell them to get bent. Or just tie them to a convenient piece of large furniture and make them watch some Wheelz. Here's footage of Aaron scoring a double backflip just in case they don't get it the first time ;0)