If you're dating person A, and person A begins to date person B...
Do you naturally assume that your time, energy, etc, with person A
will decline and/or that person A will pull away from you? Or do you
generally assume that these things will remain relatively constant,
with the understanding that if things take off between A & B that
there may well be some NRE to dissipate?
Conversely, if you are dating person A and you begin to date person C,
do you plan for or expect that your time, attention, and/or energy for
person A will necessarily decline? Or do you tend to assume that your
relationship with A will remain more or less consistent as you begin
to add the new relationship in to your life?