One thing at a time
Two things cannot happen at once; it is impossible. It is easy to imagine that two things are happening at once, because our journey back and forth between the two may be very speedy. But even then we are doing only one thing at a time. The idea of mindfulness of mind is to slow down the fickleness of jumping back and forth. We have to realize that we are not extraordinary mental acrobats. We are not all that well trained. And even an extraordinarily well-trained mind could not manage that many things at once - not even two. But because things are very simple and direct, we can focus on, be aware and mindful of, one thing at a time. That one-pointedness, that bare attention, seems to be the basic point.
Chogyam Trungpa