Let's have some fun today....! Start every step that you take up stairs to day with the foot that you wouldn't normally use! Catch yourself the first time you go up a step today, see which leg starts, and then for the rest of the day make a point of starting with the OTHER leg.
It's a really interesting insight into your movement habits and also how easy (or not) you find it to change them.
Why does it matter?
Doing this exercise matters for two main reasons (other than just pure self awareness). Firstly, if we always use the same foot to start a step up then we have a deeply ingrained pattern of one leg leading a lifting movement and one leg following it. It means that this side of our pelvis is unconsciously 'more ready' and ever so slightly forward of the other, meaning imbalance. If you never do anything to address this (stretching, yoga, pilates, balance work etc) then this repetitive pattern may be what leads to niggles, pain, injury etc in the future. Consciously changing it every so often can be enough to reboot things.
At another level, by asking your brain to do something different (which you are doing because movement ultimately originates in the brain), you are connecting into a different area of it from the normal habitual section. This opens the brain up to the possibility that things can change and can be different. So while you are focusing on 'just' changing the habitual lead leg, your brain is unconsciously realising that ingrained habits can be broken (so increasing the possibility of those new fitness, health, lifestyle habits becoming part of your new routine)