When you become tired, you want to quickly finish so you can
quickly sleep, so you have more energy and motivation, I guess? Not
necessarily mindfulness. But then if you really want to get
something done, it may be natural that you become more attentive in
your doing. I don't know but you can observe yourself whether you
are mindful or not mindful.
But if you don't even know whether you are mindful or not mindful,
then probably you are not mindful enough.