Surprisingly enough, usually it’s not all that different than not being disabled. You wake up in the morning, have breakfast, go to work, possibly go out with friends in the evening or pursue a hobby.
The devil lies in the details.
If you’re a wheelchair user, getting to work may require taking a sub-optimal route just because the fastest one has a nasty little flight of stairs on the way with no ramp beside them (so much for wheelchair access). When you’re blind, picking out your outfit for the day may be a little more tricky than for the rest of us because you have to remember the colors and patterns of all the shirts currently in your closet instead of just looking at them to figure out which one goes best with that pair of green trousers you’re wearing today. For a person with some hearing impairment, ordering a pizza over the phone may not be as straightforward as we believe it to be.
The bottom line is that disabled people are like all other people – they just have to do certain things in ways we’re not used to seeing them done. Some (e.g. using wheelchairs) are pretty obvious, but there’s a whole range of little things that most able-bodied people never even dreamed of.
To give a real-life example of the sorts of non-obvious differences disability may result in, here’s a little anecdote.
A while back, I had an ardent argument with a friend who was surprised that with my acute hearing (a common trait among the visually impaired – by the way, contrary to popular belief, this has nothing to do with blind and low-vision people being blessed with the gift of excellent hearing – it’s just a matter of learning to compensate the hindered sense using another one) I couldn’t hear him well when in a subway train while he understood me perfectly. I suggested that the problem probably lied in the fact that when I listen to somebody I just listen to them (and there’s plenty of noise do filter out when you’re in the subway) while when people without a visual impairment listen to others they also tend to subconsciously lip read. He didn’t believe me in the least (“Lip read? I don’t lip read!”) but agreed to do a little experiment in which he listened to me with closed eyes. Guess what, suddenly it turned out both of us were experiencing exactly the same subway train hearing problems :).
The audience of my accessibility related training sessions often experienced similar “eureka moments” when I made them do something as if they were disabled.
These little, seemingly unimportant differences in interacting with the world around us are exactly the sort of things you need to be aware of when working on making products accessible.