I considered myself disabled when my health conditions prevented me from living my life normally, and I have had to make big changes to how I manage even small tasks.
DLA asks... can you prepare a meal? Well, yes.
But at my worst it's heating something in the microwave for the kids, trying not to vomit and feeling thoroughly sorry for myself. Actually, maybe my worst would actually be me vomiting and my DD calling someone to come round, and them making the microwave meal for her. But that is simply heating through stuff, what I consider to be cooking, chopping vegetables and meat, making rice or pasta, I can't do them without adapting my methods - either buying pre-chopped (more expensive) or having my PA do the chopping, and forget being able to lift a boiled kettle or a pot of boiling water with pasta or rice in it. Even on a good day, not without risking cutting myself or showering myself in boiling water, so I consider myself disabled.
DLA asks... can you walk? Well, yes.
But at my worst we are talking from room to room at home, limping and taking maximum pain relief, sleeping more than usual because I get exhausted and it also helps me to manage pain. Usually I can manage to carefully split my day, and week, so that the very important tasks get done, mostly school runs and food shopping. With use of buses, and by pacing myself, leaving time to sleep afterwards between activities. If I don't, then walking becomes very difficult, I get unsteady on my feet and prone to falls, and sometimes I can faint from being in pain (usually at the school, they're used to seeing me recovering in reception).
If I can carefully manage my life, it can be very normal and fulfilling. I can go to the swimming pool every other day, I can do the usual mum stuff, I can go out on a night out every so often, I could even work. But that doesn't mean I am not disabled. Just that I am managing my disability well.