I have noticed being married to my primary seems to cut the patience for new partners negative traits and major downswings preety much in half.
And the longer you stay married, the shorter that patience gets as well.
Its not that that I feel I care less for the new partners, but that I'm more aware that I have more of a permanent emotionally support aside from them which makes it easier to walk away from someone who is becoming too large an investment of energy with very little positive outcome rather than dump more energy and time into a potential interpersonal sinkhole of a relationship.
And oddly in my case Its allow me to sidestep potential relationships that would ultimately end of being nothing but trouble before I trip headlong into NRE-land. (Used to actually be a bit of a problem of mine)
Its not malicious, at worst its just a flavour of positive cynicism.